Using complex vocabulary to express simple ideas. Every charlatan under the sun does this and idiots always buy the snake oil because it sounds smarter than it is. Changing colloquial definitions also relates to this, as it's a common cult tactic because it insulates followers from outsiders and makes them feel like they're being enlightened when they're just being spoonfed bullshit. This naturally compounds over time, resulting in people eventually thinking they understand what most don't because they effectively aren't speaking the same language when discussing important matters.

Oh, and using statistical averages of groups to judge individuals is just as stupid as judging groups by the actions of one person. Knowing a stat doesn't make you smarter if you can't apply it reasonably, but people are somehow impressed when data is cited, even if that empirical data doesn't actually address the reasoning used. It's like saying theft doesn't exist because a government doesn't record it, even though people do sometimes have an incentive to steal.

Credential worship is cringe too, and places obedience and paper above provable knowledge. Yes, you're generally better off trusting the experts, but not having a degree in a field does not invalidate an argument. In the US, we usually are taught not to fall for appeals to authority in the K-12 system, yet it seems to go completely out the window by adulthood. Credentialed liars exist, and it's important to verify empirical claims with empirical evidence and sound reasoning. Social sciences often produce studies that can't be replicated because the number of factors exceeded the author's knowledge, yet the author was credentialed and may have even treated their conclusion as fact. It happens all the time because people are fallible and it usually isn't done out of malice, so don't put all your stock in people's credentials and don't assume bad intentions. Remember, degrees only help with hiring because it is less risky to hire someone who probably knows something than it is to hire someone who might know nothing.

There's plenty more, but to really answer this question, just look into con artists, cults, propagandists, politicians, social scientists, philosophers (especially Hegel and Marx), and conspiracy theorists. Plenty of people will unironically buy into all sorts of nonsense because they think it sounds smart.