Agreed. I do wonder about a nature vs. nurture element to this, though. How much of this is who they really are, and how much of it is their daily, hourly immersion in the alternate universe?
I've done a lot of reading on the subconscious. Mania, or whatever you want to call this, can be the result of a combination of things -- such as an initial core belief system, and then intellectual isolation (or an "echo chamber") that maintains, nurtures and amplifies the belief system. That creates a subconscious template that allows a person to believe almost anything.
This alternate universe is now a fully separate, fully self-contained, fully functional ideological ecosystem in which these people can exist, protected by the internet and the stratification of cable teevee. We're not sure how to deal with this, because we've never seen anything like this. The Europe of 80 years ago was child's play compared to this, because they weren't nearly as submersed as these people are now.