It's quite genuinely a cult. Here's a good radicalization theory as to how some of them might fall into it.

I suspect a similar path could be responsible for people who become deeply involved in authoritarian Marxists-Leninism.

That's quite the leap to make, particularly when the more obvious & universal explanation is people are too easily manipulated by bullies & the the fear of social ostracism that runs so deep to their core that they aren't even consciously aware of it. It's a human thing, not anything uniquely American - there are plenty of similar examples of this happening elsewhere as we speak.