Why are conspiracy theories popular?

People who feel powerless or vulnerable are more likely to endorse and spread conspiracy theories. This is seen in online forums where people’s perceived level of threat is strongly linked to proposing conspiracy theories. Conspiracy theories allow people to cope with threatening events by focusing blame on a set of conspirators. People find it difficult to accept that “big” events (e.g., the death of Princess Diana) can have an ordinary cause (driving while intoxicated). A conspiracy theory satisfies the need for a “big” event to have a big cause, such as a conspiracy involving MI5 to assassinate Princess Diana. For the same reason, people tend to propose conspiratorial explanations for events that are highly unlikely. Conspiracy theories act as a coping mechanism to help people handle uncertainty.

Stephan Lewandowsky & John Cook, The Conspiracy Theory Handbook