Missed one of the big studies done recently: If you believe in one conspiracy theory, you're likely to believe in multiple, contradicting conspiracy theories.
Conspiracy theorists, then, are people who doubt for doubt's sake. There's a distrust in the official narrative and therefore, non-official narratives are given higher status simply for being non-official. Combine those two - a preference for the minority opinion and a snowball effect where doubts multiply - and you end up with a lunatic fringe pretty quickly. that is what we've all been acknowledging for centuries without really putting into words: if you doubt a few things, you're rational. If you doubt everything you're nuts.
Elvis is alive. Princess Diana is alive, or the Queen killed her because she was pregnant and converting to Islam. Anna Chapman, CEO of PropertyFinder LLC, was a Russian spy. Fidel Castro shot JFK. The CIA hired mafia assassins to kill Fidel Castro. George Bush planned 9/11. The Jews planned 9/11. We all mass-hallucinated 9/11
1) Anna Chapman pled guilty to "spying lite."
2) Robert Wallace, former head of CIA OTS for decades (basically "Q"), describes - at great length - assassination methods and devices intended to be deployed against Castro in his book Spycraft. he also devotes a chapter on the ingenuity of a group of CIA operatives captured in Cuba for undisclosed reasons who spent several years in a Cuban prison and eventually led an uprising.
So yeah, there's some conspiracy theories. Then there's "conspiracy" theories. I mean, wikipedia. Mixing stuff revealed by the Church Committee in with "elvis is alive" kind of denigrates the subject.