Jesus was a delusional rogue rabbi whose mother Mary was an adulteress and father Joseph a cuckold. His whore mother put into his mind since he was a young child that God was his "real father" and that he was a very special boy. Jesus grew very knowledgeable about the Old Testament, began to believe that he was the "Emmanuel" whom Isaiah spoke of and so he sought to fulfill the prophecies as the Messiah which he studied.
He was an apocalyptic preacher whose teachings were never meant to be written down, in fact, he announced the end of the world as being imminent and told people to give up everything and follow him; he stated that his generation was to witness it all. He was crucified, died and, of course, never rose from the dead, but his closest and most faithful followers convinced themselves of that lie and went on to preach, converting many.
For several decades following the decomposition of Jesus' corpse, stories and legends about him were spread by word of mouth before some of them were selected and written down, thus leading to the Gospels whose anonymous authors mostly copied each other. Then came Paul, an energetic and zealous repentant ex-hunter of Christians who claimed to have a vision, joined the apostles and wrote the bulk of the New Testament, introducing many teachings of his own, hence the term "Pauline Christianity". Without him, Christian theologians would be helpless.
Since Jesus appealed to the uneducated, illiterate and lowly people which constituted the overwhelming majority of the Roman Empire, his death cult spread like wild fire. The roman government, being opportunistic, eventually made it the official religion thus cementing and validating its existence. Due to this, nations grew culturally with Christianity at their core and so it has lasted to this day, aided by theologians' relentless mental gymnastics, colonialism, as well as teachings of repentance, redemption and paradise after death which attract the emotional human mind.
