But religion is not just ideas either. You may have a very nicely written AI-generated "bible" but does this kind of idea gain traction solely on its textual merits? I think it's rather complicated.

Certainly if your religion captures the leadership of a large Mediterranean empire, that would help. But does that idea win because it's a good idea? Very hard to say. It took a long time to capture Rome, and it's not clear that this is simply because St Paul and co had better ideas.