I consider Christianity, in its least distorted form, to be a wonderful movement for spiritual development.
I attribute the rise of Christianity to changes in the mental and consciousness of the masses of people, cultural changes, political influences, a side effect of wars and conquests and migrations and other accompanying frictions and mutual influences, over several centuries.
I believe that the most significant influences that caused the emergence of Christianity came from three civilizations: Roman, Greek and Egyptian.
Rome: the figure of Julius Caesar, who was a sort of messiah for the people of the time. As a brilliant politician and military man, from the Romans’ point of view he was a “God-sent Messiah” leading the Roman Empire to triumph, prosperity and freedom from external invaders.
Egypt: Monotheism, thanks to Echnaton. Specifically, cosmogonic monotheism, with one sun god as the common source of all things and who can be referred to simply as the One God.
Greece: Plato and Greek philosophy. And in particular love, which was called agape. Agape was the highest form of love. It meant the love of God for people, as well as people for God. It was also an unconditional and transcendent love.
In addition to this, I believe that along the way there were at least a few select people who pushed these religious transformations forward. Like Saint Paul and Jesus himself, of course.
In the end, beyond the historical complexities, which are impossible to pinpoint anyway (at least for me), the most important thing is the one general idea behind Christianity, which in one sentence I could present: The unconditional love (“Greece”) through conception of oneness (“Egypt”) and perseverance, courage and strength of character to stay in faith on that path (“Rome”). At least I perceive it that way…