I was raised in a hardline Calvinistic Baptist worldview with some similarities but in the UK. While our version of this madness is a bit less politically extremist (since it’s such a minority viewpoint) and there’s a few beliefs like the rapture which are peculiar to the US I think I can say with some experience that fear is a big part of it. Fear of ‘eternal conscious torment’ is a powerful motivator when you’ve literally been taught from birth that the most important thing is that you’re ‘born again’ so you’re not tortured beyond the ability of the English language to express for eternity after you die. In our case this was entirely out of our hands too, god predestined you for bliss or burning before the beginning of the universe and that was that.

Think of it like all forms of totalitarianism (and it absolutely is totalitarian in the sense of ‘you must bathe your very being in our elaborate ideology, surrendering to it completely both inside and out’), under such circumstances a small number of people absolutely revel in being empowered to punish others and be the bearer of ‘difficult truths’, another small group actively rebel against the ideology while often deeply internalising large parts of it anyway because you uncritically absorb what’s around you as a child, but the vast majority of people just keep their heads down and try to stay out of trouble which is surprisingly hard in a world where god can see your thoughts and is judging you for each and every one; especially the intrusive ones. Julian Jaynes would have been fascinated by this world, it’s a deep insight into the power of the human brain to bend perceptions around beliefs. We all do this as part of being human secular or religious but this is a very clear example of the phenomenon because of how little the belief complex has to do with objective reality.

Also people who’ve not undergone it have no idea what indoctrination actually entails a lot of the time. I consider myself to have been indoctrinated but most of that process was actually really pleasant! It’s not having your eyelids forced open while unspeakable horrors unfold on a screen it’s having fun bonding experiences with friends while absolutely poisonous ideology is drip fed to you over the course of years so slowly you don’t even notice.