We don’t know the answer to the question, though society would surely be better off if there were no conspiracy theories. Maggie Koerth-Baker’s NYT Magazine essay looks at some of the research. Typically in psychology the results are fuzzy:
Conspiracy theories also seem to be more compelling to those with low self-worth, especially with regard to their sense of agency in the world at large. Conspiracy theories appear to be a way of reacting to uncertainty and powerlessness.
She ends with this summary:
(…) Alex Jones, a syndicated radio host, can build fame as a conspiracy peddler; politicians can hint at conspiracies for votes and leverage; but if conspiracy theories are a tool the average person uses to reclaim his sense of agency and access to democracy, it’s an ineffective tool. It can even have dangerous health implications. For example, research has shown that African-Americans who believe AIDS is a weapon loosed on them by the government (remembering the abuses of the Tuskegee experiment) are less likely to practice protected sex. And if you believe that governments or corporations are hiding evidence that vaccines harm children, you’re less likely to have your children vaccinated. The result: pockets of measles and whooping-cough infections and a few deaths in places with low child-vaccination rates.
Psychologists aren’t sure whether powerlessness causes conspiracy theories or vice versa. Either way, the current scientific thinking suggests these beliefs are nothing more than an extreme form of cynicism, a turning away from politics and traditional media — which only perpetuates the problem.