its not that deep

"oh, that's easy! it's because they're fundamentally Bad people who want to hurt others and choose their beliefs to justify that! :) hope this helps"

or

"they just don't have access to the same information we do. look at this person who was raised in a cult! don't you feel sorry for her?"

and like, yes, fine, some people were in fact raised in cults, but what i wish people would understand is that the bulk of it is just normal human flaws, like:

they want to believe stuff that makes them feel smart and cool and like they've figured everything out (you also do this)

they want to believe stuff that makes them feel like their emotions are justified and grounded in reality, and that the people they want to hurt deserve to be hurt (you also do this)

they form conclusions before they've processed all the relevant information, and cling to that first impression even when new info comes to light (you also do this)

they pick up beliefs from the people around them because they want to be liked and fit in, not because the beliefs are good or true (you also do this)

they come up with reasons that the stuff that benefits them (and the people they like and identify with) is actually overwhelmingly best for everyone and obviously the right thing to do (you also do this)

they pay more attention to stuff that supports what they already believe and avoid looking in places that might show them otherwise (you also do this)

they listen to people who talk like 'one of them' and ignore others (you also do this)

they come up with reasons to dismiss people with conflicting viewpoints as obviously in bad faith or ignorant or a shill or evil (you also do this)

they fail to take their own beliefs seriously sometimes, and take their beliefs way too seriously other times, in a selective way that lets them do the things they already wanted to do (you also do this)

the very ways they construct the ideas of 'knowledge' and 'wisdom' and 'belief' and 'understanding' are biased so that what they don't want to believe comes under lots of scrutiny and what they do want to believe receives less (you also do this)

you, dear reader, are presumably right about everything and were correct to die on every hill you've ever died on, but the difference between you and someone who's wrong about important stuff doesn't look like "well they're inherently evil and i'm not", it probably looks like a combination of:

natural environment (they would have been exposed to different information than you regardless of their choices)

being in the right place at the right time (your particular profile of flaws and virtues happened to be what was needed to lead you to the right conclusions, they had the opposite experience)

random luck (you doubled down on what felt right to believe but wasn't, but it turned out to be inconsequential, or even right for different reasons, while they doubled down on what turned out to be a horrible mistake distorting their entire worldview)

you do less of the things in the previous list, and over time the difference between you and them adds up

and, look, i also do these things. the nicest and most thoughtful people i've ever met do these things. if you meet someone who never does any of these things, i dunno, give them a fucking medal or something.