This is an interesting read on why people believe conspiracy theories, published in the wake of the Las Vegas shooting.
https://psychcentral.com/blog/archiv...-believe-them/
Having read this I no longer engage in arguments with conspiracy cranks as it is more than likely an issue of personality rather than knowledge or understanding of an event.
"People who believe in conspiracy theories can feel “special,” in a positive sense, because they may feel that they are more informed than others about important social and political events." - Lantian et al (2017)
Moulding et al. (2016) found that, consistent with their hypotheses, “endorsement of conspiracy theories related moderately-to-strongly with the alienation-related variables — isolation, powerlessness, normlessness and disengagement from social norms.”
van Prooijen (2016) also found that self-esteem instability resulting in self-uncertainty also is a characteristic associated with a greater likelihood to believe in conspiracy theories.