People I normally respect have bought in on some crazy-ass conspiracy theories.  Elon, Balaji, PMarca... all super smart, and all tweeting crazy shit. I did some research to see why people get hooked on conspiracy theories:
https://www.charterless.com/p/do-your-own-research-the-psychology

Writing about DAOs @ charterless.com.
Ex-FB, Amherst College.
Always an Eagles Fan.

Examples of crazy conspiracy theories (minus Elon)?

I think it would be helpful if we talked about hypotheses rather than theories. A CT sounds too settled to most folks and is quickly dismissed by citing one or two crazy examples (eg lizard people). A hypothesis would be more open to debate and exploration.