I RESPONDED IN RED.
you asked: "Why would the elect be gathered and when?"
God's very elect are his chosen people...he is choosing those souls right now...FACT...John 14:21 tells you how you know if you are chosen...HE manifests himself to you. That's answers the "when" Why are are gathered is because we are HIS army on earth before he comes...HE will send his 2 witnesses to gather us together when they arrive. From biblehub.com Mark 13:27 And then shall he send his angels, and shall gather together his elect from the four winds, from the uttermost part of the earth to the uttermost part of heaven. They are gathered by angels not by the two witnesses.
"Why would flesh be saved for their sake?" There is no flesh saved; no flesh can enter the Kingdom of God (the 4th dimension)
From biblehub.com KJV Matthew 24:22 And except those days should be shortened, there should no flesh be saved: but for the elect's sake those days shall be shortened. Flesh is saved. That is why there is a rapture.
"There is a mystery in the gathering of the elect and you don't know what it is do you?" yes, i do know what it means, and when those 7 thunders sound, i will hear HIS words for the thunder IS the voice of the Father...those who have ears to hear and eyes to see...WILL UNDERSTAND HIS VOICE WHEN IT THUNDERS....that is the mystery...because few on earth at that time will HEAR and SEE this TRUTH we are being told. From biblehub.com Ephesians 4:7 But to each one of us grace has been given as Christ apportioned it. 8This is why it says:

“When he ascended on high,
he took many captives
and gave gifts to his people.”
9(What does “he ascended” mean except that he also descended to the lower, earthly regionsc ? 10He who descended is the very one who ascended higher than all the heavens, in order to fill the whole universe.) 11So Christ himself gave the apostles, the prophets, the evangelists, the pastors and teachers, 12to equip his people for works of service, so that the body of Christ may be built up 13until we all reach unity in the faith and in the knowledge of the Son of God and become mature, attaining to the whole measure of the fullness of Christ. When Christ died and went into the earth, the elect were taken and deposited in this time for a mission. Some know who they are and some don't. The first will be last and the last will be first. This generation will not pass. When Christ was resurrected, the elect came out of the graves and appeared to many. You will see in Matthew 24 that the disciples ask him when the end will come. First he predicts the destruction of the temple in 70 AD and then fast forwards to this time. The two witnesses are referred to as two olive trees and lampstands for a reason. The life of an olive tree is about 70 years. The first was from birth of Christ to 70 AD. This time started marking the last generation or life of an olive tree in 1948 with the Israel becoming a nation again. The 70 years is almost up. The complete parousia will take care of the awakening. Why do you think Paul considers himself among the living here on earth at the end? Why do you think he says he will be called up into the clouds with the multitude at the seventh and last trumpet? The first resurrection takes place and what is left after the Great Tribulation, the last 1260 days are taken up.
From biblegateway.com KJV Revelation 7:9 After this I beheld, and, lo, a great multitude, which no man could number, of all nations, and kindreds, and people, and tongues, stood before the throne, and before the Lamb, clothed with white robes, and palms in their hands; Note he says all nations, tongues, etc. This indicated the spiritual transformation to the second Adam incorruptible spirit as in 1Corinthians 15 has not taken place yet. How do we know that? There is a flesh rapture, and the earthly distinction are still there. John is quizzed later in the same chapter as follows: Revelation 7:13 And one of the elders answered, saying unto me, What are these which are arrayed in white robes? and whence came they?
14 And I said unto him, Sir, thou knowest. And he said to me, These are they which came out of great tribulation, and have washed their robes, and made them white in the blood of the Lamb. What did he say? CAME OUT OF THE GREAT TRIBULATION!!!!! That would indicate a deliverance before the final victory for the multitude. And... everything appears to be chronological, and we haven't even gotten to the trumpets yet. You can't find anywhere in the bible that says the spiritual transformation to become of the Kingdom of the Lord is anywhere other than at the seventh trumpet. This is another event. The rapture takes place first. It says one will be taken and another left in the field. What would be the point of such a deliverance if the battle is won at armageddon by Christ and the world transformed to his Kingdom? What would the person in the field be delivered from? From biblegateway.com 1 Thessalonians 4:15For this we say unto you by the word of the Lord, that we which are alive and remain unto the coming of the Lord shall not prevent them which are asleep.
16 For the Lord himself shall descend from heaven with a shout, with the voice of the archangel, and with the trump of God: and the dead in Christ shall rise first:
17 Then we which are alive and remain shall be caught up together with them in the clouds, to meet the Lord in the air: and so shall we ever be with the Lord. What did he just say? Caught up with those in the clouds. What is already before the throne in flesh? THE MULTITUDE!!!!!!!!

Now what happens at the last trumpet? From biblehub.com KJV Revelation 11:15 And the seventh angel sounded; and there were great voices in heaven, saying, The kingdom of this world has become the kingdom of our Lord, and of his Christ; and he shall reign forever and ever. Didn't you say that flesh and blood cannot inherit the Kingdom of God as did Paul? Now the nations of the world are transformed to the incorruptible spiritual bodies because the kingdom of this world has been made what??? THE KINGDOM OF THE LORD.
God became man and walked the earth...HE was the spiritual body living in the flesh temple body of his SON, Jesus Christ....God followed his plan for this second earth age...all 12B souls he created in the first earth age in heaven (the 4th dimension) which was billions of years/eon of time...wherein at the same time in the 3rd dimension all that was here were dinasours...then the rebellion/war in heaven when Satan, the most beautiful, most intelligent cherebum the Father created, decided he was smarter, more powerfull that Yahvey, EYA ASHA EYA HEBREW meaning (i am as i am)...for the mercy seat was protected by Satan and Michael///that seat was ordained for Christ, his seat...Satan decided it was his seat and sat on it, Michael threw him and his followers out of the 4th dimension into the 3rd dimension...That is written Genesis 1:2...Genesis 1:1 is the first earth age...the Father did not create the earth VOID and dark...it became that way from all the energy cast into this dimension, broke the earth apart and flooded the earth...and then God began again, creating this second earth age...HIS PLAN BEING; ALL 12B SOULS HAD TO PASS THROUGH WATER BE BORN AGAIN (BORN FROM ABOVE THE 4TH DIMENSION---is what the original manuscripts read)...
So in answer to your question....God followed his own plan, using Mary to birth his ONLY BEGOTTEN FLESH BODY, Jesus Christ, housing God Almighty's spiritual body... Luke Chapter 1 through Chpt 3 tells you all about the genelogy of Christ....YOU SEE SATAN HAS NO GENELOGY BECAUSE HE REFUSES TO BE BORN OF WOMAN.

you need to review Book of Peter 1 and 2....peter tells you all about the 3 earth/heaven ages...gives you a clearer picture of HIS PLAN.

Final question "You still have no explanation for what happens in Revelation 6 and 7."

Revelation 6 describes the seals...

Revelation 7 declares the 4 angels have to hold back the 4 winds (end of this earth age) until all 144,000 of the decendents of the Nation of Israel have to be sealed...meaning have to be shown that Christ was the flesh temple body housing the spiritual body of God Almighty...and that when Christ died on the cross, rose in his flesh body and walked the earth for 40 days/nights...then went to the 4th dimension, 10 days later, the Holy Spirit (spiritual body of the FATHER) came back to earth and traverses the earth just like the spiritual body of satan....both entities pulling you toward them...except the Holy Spirit watches what you do when satan tries to tempt you to do wrong....if you resist, the Holy Spirit moves closer, the more you resist satan's spirit, the closer the Holy spirit gets to you...then booom the Holy Spirit surrounds you and he will never leave you nor forsake you.....THIS IS THE WAY IT WORKS...i tell you the truth....believe it or not...it's your choice..the Father gives us FREE WILL to chooose who we want to follow...satan or Christ, the choice is yours....i'm sent to those who want to learn...it's up to you to find Christ in you life....i put you on the path...the rest is up to you. AMEN
The 144,000 remain on this earth through the Great Tribulation. They follow the worthy lamb forever. They live at the base of Mount Zion, the holy dwelling place of God. Read Ezekiel 37 for confirmation. The twelve seed tribes are the rightful heirs to the Kingdom. The Union Jack is a clue to the spiritual war. It is the Union of Jacob and the defeat of the lineage of cain and the antichrist. This is symbolized by the cross breaking the x on the flag.

You are getting caught up in ages that are going to end. The New Heaven and New Earth will come down and the old will flee. All that is without a name in the Book of Life will be thrown into the lake of fire. The trial by fire Peter speaks of and the baptism by fire spoken of by John the Baptist/Elijah in Matthew 3:11 are important.