many conspiracy theories, JFK ones in particular, are tools that people use to rationalize the terrifying amount of disorder that still exists in the world. it's frightening to think that one man as simple as oswald could affect the entire world the way he did, somehow it's more comforting to blame the mob or the CIA or the russians. i think this idea fits with what felix rex said, people would rather blame a dark and highly organized cabal than admit that an individual mumped up and got people killed.