Why do we find conspiracy theories compelling?
First, humans get a pleasure response from doing survival related things... hunting, growing things, eating, having sex, solving puzzles, recognizing patterns and building things. Our advancement as a species is directly related to the fact that we love to do these things even *beyond* what is needed for survival.
As bizarre as it may seem, the compulsion that gives us science also gives us conspiracy theory. We are hardwired to seek out and make sense of patterns of every sort. The more complicated the pattern the better.
Secondly, there is something utterly seductive about having knowledge that other people do not have. You'd think, logically, that if most people are satisfied with a mundane or obvious version of events we'd question our more elaborate version... but we don't. It's riddiculously easy to believe that all the experts are wrong/compromised/in on it, if we can believe in our own greatness at the same time.
What brought this up? Public access television. It's useless to argue with the conspiracy theorist because opposition to conspiracy is the basic proof of it's truth. I think that's part of what makes it so maddening.