Let's be clear: i'm not saying conspiracies doesn't exist. By conspiracy theories, i mean the plots whose existence is at best highly unlikely, at worst totally senseless, notably if:

-They are breaking the laws of physics.

-They are too costly (logistically and/or financially) to be profitable.

-They are defended by untrustworthy sources (populist or cult leaders, random people, celebrities without expertise in the concerned domain, parodies taken seriously,...).

-They are often involving far-right's scapegoats.

-They are involving a large amount of people.

-They reject science by principle.

-The interests of the supposed conspirators are unclear or incoherent.

-Their so-called proofs are incoherent, manipulated or are proving nothing at all.

-They would be funny if they were published as parodies in The Onion.