Under conditions of fear or anger, as for example following a bad event, people want to find a cause, and they also want to resolve their own uncertainty. So if you’ve seen an assassination or a terrible economic downturn or a missing plane, there may be an inclination to posit an agent who’s behind it. Another thing is, if you have social networks where people are communicating with each other, especially with like-minded others, then you can see conspiracy theories going viral. Some of us have a disposition to believe in conspiracy theories. That’s just a tendency some people have. Finding a conspiracy behind something sometimes has some of the attraction of solving a puzzle.