I think political motivations have a lot to do with many conspiracy theories. The former Soviet Union used to spread disinformation about the US on a regular basis. One such claim what that the US invented AIDS in a lab and deliberately released it to the population. There are a lot of people around the world who believe this.

There are also those who see everything through the prism of their political biases. During the Clinton years, there were one set of kooks who claimed Clinton was behind a rash of "suspicious deaths" and even maintained the "Clinton Body Count". During the current administration, BDS sufferers automatically see a conspiracy behind everything the president says or does. This is by no means limited to the US, either. If you're predisposed to assume that the government is wrong or evil (especially when your side isn't in control), then it isn't a stretch to believe conspiracy theories.