From Scientific American:
Conspiracies do happen, of course. Abraham Lincoln was the victim of an assassination conspiracy, as was Austrian archduke Franz Ferdinand, gunned down by the Serbian secret society called Black Hand. The attack on Pearl Harbor was a Japanese conspiracy (although some conspiracists think Franklin Roosevelt was in on it). Watergate was a conspiracy (that Richard Nixon was in on). How can we tell the difference between information and disinformation? As Kurt Cobain, the rocker star of Nirvana, once growled in his grunge lyrics shortly before his death from a self-inflicted (or was it?) gunshot to the head, “Just because you’re paranoid don’t mean they’re not after you.”
But as former Nixon aide G. Gordon Liddy once told me (and he should know!), the problem with government conspiracies is that bureaucrats are incompetent and people can’t keep their mouths shut. Complex conspiracies are difficult to pull off, and so many people want their quarter hour of fame that even the Men in Black couldn’t squelch the squealers from spilling the beans. So there’s a good chance that the more elaborate a conspiracy theory is, and the more people that would need to be involved, the less likely it is true.
Why do people believe in highly improbable conspiracies?