I appreciate your ability to separate sharing the belief itself from approval of acting on sincerely-held principle. However, I think the danger is much more plausible than you do.
First, and least important, consider that self-replicating, solar-powered factories aren't magic; they're algae.
Second, and more important, consider this fully non-magic route to doom:
- We continue putting AI in charge of more things
- It continues to get more capable, more eval-aware, and more prone to doing odd things, in service of goals that humans didn't intend to inculcate in it
- Eventually, enough of the economy depends on it that we couldn't turn it off, any more than we could turn off the faber-bosch process or cargo shipping
- AIs start doing something we can't survive, but less acutely than we couldn't survive turning them off. Everything else we try seems to work at first, but quickly loses effect
- Game over