Possible : "Jeshua ben Josef" was a truth-searcher. Started as a frum jewish reb that wanted to dig deeper into scripture, nature, medicine and mental powers. He knew Torah in and out, he often speaks of it in the so called "New Testament".

Sadly over time he mixed the beliefs of jewish religion with his very own interpretation of reincarnation ( which catholics again misinterpret as "holy ghost" ) and packed this mishmash into parables and went completely nuts in the end by referring himself as being Moshiach. ( "christ" / "Messiah" ) although he simply could not and can not be, cause he does not fulfill the requirements to be so, but that is a story on its own.

Would he just sticked to one thing, priest, medicine man, nature healer.. nothing would have happened. But the mixture of his teachings ( or what his disciples made of it ) lead to what finally happened.