How Account for the Success of Christianity? Another point, apropos of what some other posters have stated:
Christianity combined Greek philosophy with Jewish law and order. The God of the Old Testament is rarely omnipotent or omniscient. He often is surprised by his people (hardly demonstrating omniscience). He seems to want to favorably compare Himself to competing Gods ("You shall have no other Gods before me").
He is also often masterful and poetic, even when He is tormenting Job he trenchantly asks him,
“Where were you when I laid the earth’s foundation?
Tell me, if you understand.
5 Who marked off its dimensions? Surely you know!
Who stretched a measuring line across it?
6 On what were its footings set,
or who laid its cornerstone—
7 while the morning stars sang together
and all the angels[a] shouted for joy?"
The New Testament God sends His only son to save mankind (although we might ask, "Who was it that set us up to fail?") Jesus represented God as philosophical - but not in the Greek, logical way. Instead, He is a story-teller, and a myth-maker. Ethics, for Him and for Christians, is not logical, but analogical. "What would Jesus do?"
So Christianity combined Jewish law with Greek philosophy, and added an analogical touch.