The real Jesus was a Jew, the leader of a radical revisionist movement within Judaism. It seems improbable that he had any intention of founding a new religion. But after his execution, ordered by a combination of Jewish priests and Roman officials, the Jesus movement rapidly evolved into an independent religion, persecuted and protected by the Roman state. By the end of the fourth century, pagan rites had been banned and Christianity had become the official religion of the Roman state. Religious allegiance followed political power.
Religions create, and thrive on, passionate commitment and passionate conflicts.
Jesus is a symbol both of devotion and of disagreement. Pagans and most Jews thought that it was absurd to claim that Jesus was the Son of God. And early Christians disagreed fervently among themselves as to whether Jesus was wholly divine, or wholly human, or a subtle mixture of human and divine. Modern believers have tried to forget these ancient debates, and have largely succeeded. But these were only some of the beliefs which early Christians died and later killed for.