I think one thing to consider is the utility of a religion. Christianity is a pretty clear and useful religion. 10 rules to live by. One god. Everyone’s welcome. Forgiveness is given. I’m simplifying things a lot, but you get the gist. All this makes the whole thing pretty easy and attractive, right?

Obvious utility and usefulness is highly dependent on the situation. A big hammer is a very useful tool, but not so useful when you’re dealing with intricate crystal sculptures.

So I think Christianity just happened, or was designed, to be usefull at the time.