1. Many people find it impossible to believe that a few utterly unimpressive individuals can do so much damage. Lee Harvey Oswald, a man who can best be described as simply a loser, could change history all by himself? It doesn't seem to make sense.
2. Many people want to blame those they loathe for as much of what they do not like as possible. Just about everyone who believes in hidden conspiracies attributes those conspiracies to those they hate. People who hate President George W. Bush blame him and his administration for 9/11. Egyptians who hate Israel have blamed AIDS on Israeli prostitutes. Indeed, attributing to Jews hidden conspiracies -- the "world Jewish conspiracy," the "Protocols of the Elders of Zion" -- is the oldest and most common belief in a hidden conspiracy.
3. One should never underestimate the power of boredom -- and the subsequent yearning for excitement -- to affect people's thinking and behavior. Belief in a hidden conspiracy is far more exciting than accepting prosaic truths. Figuring out the "mystery" of who killed JFK is a much bigger thrill than accepting that one jerk was responsible. Deciphering who was "really" responsible for 9/11 is a lot more interesting than accepting that 19 Arabs with box cutters did it.
4. People who feel powerless over their own lives are far more likely to believe that some invisible force controls their fate than people who believe that they are the masters of their lives.
5. There is, apparently, a great yearning among many people to believe that there is hidden knowledge and that they have access to it. It makes them feel special, perhaps even superior to the rest of us who do not have access to this hidden knowledge.
6. In Western societies, it appears that secular people are more likely to believe in hidden conspiracies than the more religious. It may be that the religious already believe in an invisible power that governs the universe -- God -- and therefore seem to have much less of a psychological or emotional need to believe in invisible powers on earth.
Whichever reason or reasons apply, the bottom line about those who believe in hidden conspiracies is this: They choose to believe in them. Their psyche, their emotions, and/or their political agenda bring them to their belief in a hidden conspiracy. Never the facts.