Algorithms reward extremism. Every major social media algorithm takes what you're already consuming and tries to find more of it. Ergo, the more things your content is "more" than, the greater audience pull you'll get. This is basically what created the alt-right, or the intellectual dark web, or whatever you want to call it. Attention economies naturally produce more extreme views because people are monetarily incentivized to become more extreme. This isn't a new thing, we saw this much earlier in different ways with radio hosts like Rush Limbaugh and Alex Jones, just as with most things, the Internet and social media cranked it up to 11.
To what extent they "really believe it" is between them and their supposed god and I wouldn't speculate on it. I'm sure many do. I'm sure many also turn the camera off and say "thank fuck we're done for this week" then resume a relatively banal existence. Both however are corrosive to society.