I'm fairly certain that the indulgence in conspiracy theories requires the employment of circular logic to maintain.
At the least, it requires dubious truth claims and inferences (thus compounding the error in the logic) in order to make each successive leap.
It requires motivation, intent, and what could have happened, since the truth is, by definition, inaccessible.
Once you've accepted one of the premises, you're now on the circular logic merry-go-round!
How to combat this?
Separate each truth claim and examine it individually. Don't relate it to other truth claims. Establish the veracity of a single, well-defined question.
Make sure each claim is well-defined and causally linked. Don't settle for vague assertions or possibilities. Either a thing is true or it is not true.
Claims must be falsifiable!
You don't have to resort to:
Trust/mistrust of the "wisdom of the crowds"
You should liberally apply Occam's Razor - simpler explanations are by definition better.
Surprising explanations bear more burden of proof.