I've got an old friend like this. I've posted about him before. We grew up across the street from each other, and were closer than brothers up until around the middle of high school when we went our separate ways. He was one of those guys that would get interested in something and consume any and everything he could find on the subject and have a masters level of understanding of it in about a week. He was in honors everything, in the school G&T program, magnet middle and high school, all of that. He was also kind of socially awkward, as those types usually are. We lost touch after my grandparents passed and I moved away from Port Arthur. He found me on FB 6-7 years ago, and at first I thought he had been hacked by a Russian Troll account. He grew up to be literally the worst person imaginable. Everything is the fault of the evil democrats and their jew masters. He's a "pastor" at some strip mall Pentecostal church in the DFW 'burbs, has like 5 kids, and spends most of the time at his blue collar job posting conspiracy theory memes about the Clintons, Covid, Epstein, globalists, gun pr0n, etc. He's so prolific I occasionally have to mute him for 30 days for my own sanity. The only reason I don't block him completely is his parents mean the world to me, and they're in their 80s and 90s now, and I'd for them to pass and not know it.
Fast forward to a couple years ago, and I got paired up at work with an engineer with Autism. He was so frustrating I was ready to quit after a few weeks. I ended up learning a lot about Autism Spectrum Disorders in an effort to figure out how to work with the guy, and one day it hit me..."Holy shit, my childhood friend is autistic". Both guys are 100% sure of their intellectual superiority and neither one of them has a bullshit detector, so if they learn something through their own research it's almost impossible to convince them they're wrong. Add in the social awkwardness and hyperfocus and it's a ripe target for conspiracy shit.
TL;DR, lots of undiagnosed Autism in conspiracy circles.