I mean, if they didn’t, then they probably would be religions, just “stuff everyone believes or has reasoned discussions about”.
Spoiler: they can’t all be right.
However, if I were to take a guess, it’s something like “people sometimes believe things without proof”. But obviously this is not true only of religious people, other people have their own creation stories – the sole difference is their’s don’t involve worship. And I agree they can’t all be right, but perhaps one of them is.
These are axioms, you cannot derive them, you can only derive from them. Saying “my axioms are rational, yours are ‘insane’!” is frankly childish, and speaks to a deep lack of understanding of the essence of reason.