People are all different, so the reasons for them believing in conspiracies cover a broad range of factors. In general, though, people tend to believe in conspiracies because of helplessness.I found that belief in conspiracy theories is strongly linked to insecurity about employment, alienation, lack of interpersonal trust, and minority status ...
First and foremost, we have to ask ourselves why are there conspiracy theories in the first place and the answer that comes to mind is that, it's mainly because the government are not truthful about everything at all, when one hides secret, it makes other develop their own side of what they deem to be true themselves.