I'm deliberately writing this in this abstract level, because it's not just cults who get their members like this. Extremists employ the same tactics, as does the military, many influencers, self-help as an industry, and even a lot of cheating in relationship happens for the same reason.
The takeaway, I think, is that these bad things happen to normal humans, same as everybody. And the second one is that it really pays off for the individual to look inside, so that nothing festers unchecked. Many of the funny things happen in the dark corner where we're not willing to look.
I do not blame religious people, though. It is easier to be a believer and have pre-made and comfortable ideas about why you are here and what will happen after you dire than to think that you have a mix of happiness and despair in your life and then it's over.
It's a struggle for me, though, so at the end of the day I'm a mix of judgmental feelings and some conscious empathy. I have learned that when I shut down curiosity with judgment, then I get no further in the topic, but I have strong feelings too, against religion in general for example. Organized religion has not been doing a good job at being morally superior or supportive of the people, despite this being on the forefront of the organizations. Turns out that they behave exactly like how other power structures do, and even if they give some existential comfort at all, they take a lot in return.
Your other point is also well worth of consideration. Being educated doesn't mean that one is not susceptible to whatever false narrative, be that a cult's teachings, or the flat earth movement. It turns out that life is complicated, and just because people are good at one part of it, they can suck at another. It's like many of the facets of life don't have any "cross-talk" at all, you have to pay attention to all of them and "level them up" independently.
And yeah, taking a pre-made idea is pretty attractive, instead of having to deal with all of this all the time. We don't create our food from scratch either, after all.
[0] https://www.psychiatrictimes.com/view/laziness-does-not-exis...
[1]: https://en.wikipedia.org/wiki/Scientology#Demographics [2]: https://youtu.be/xSlYVGNQiFs
Its emotional not rational.
As another sibling comment says, it's how radical and terrorist politics works too. Emotional need for belonging.
Also there is a reinforcement loop where the outside says "you are wrong" and inside they say "the outside hates us".
They also make it clear that the love will be taken away the minute you stop obeying them.
Also it is much easier to accept views of the skilled salesman than think by yourself.
They are as susceptible to manipulation tactics too.
At this point any "new" members are going to be mainly made up of people born into it, or without internet access.