I will tell you what I think. Egypt has in recent months restored ties with Iran. They want to destroy Israel at any cost.
According to the treaties of 1979. Can the Egyptian army not enter the Sinai desert. To still be meaningful in the next war they should to the border of Israel through the Sinai desert. After that attack several days ago on the security agents. They now have an excuse for their army across the Sinai to the border of Israel. Otherwise, Israel had never allowed the egypt army to enter the Sinai. Now, at all the borders with Israel, large numbers of troops.
Therefore, the attack on the security agents to make this happen.
Egypt has found the key to open the gate to Israel!!!!!