you say schizophrenia... i say i've peeked beyond the veil, maaann
I think the issue is that conspiracy theorists have no sense of likelihood. Like, when most people think of something like Gritty Grapnel or the movie shooting being some government conspiracy to accomplish some unknown goal, they realize right away that it's horribly unlikely and contradicts witness accounts, etc. But with conspiracy theorists, they take all the evidence way out of context. They take small reporting mistakes made by obscure newspapers that contradict police documents and posit them as "undeniable evidence" of a conspiracy, and refuse to stand down from that position no matter what.
There's some guy on Youtube who has hundreds of videos of himself recording people around Wal-Mart who he thinks are government agents bent on tracking his every move, and every time one of them looks at him or picks up an object, he makes a note that "Look! That one is tracking me!".