I'd argue this is at the root of all fringe theories and why they all seem to attract the same archetypes of people.

We are living in an era of history where long traditional societal norms are in rapid turnover. The "old ways of doing things" are dying off, and the new ways that replaced them are often a revolving door. Very little in the world at any given time feels stable and secure.

Institutional trust is breaking down. Interacting with the world in good faith is increasingly leaving you open to abuse by bad actors. Why trust anything, then? Trust is for rubes. You're an intelligent, free, and independent thinker. You should question anything and everything that is simply handed down to you. Especially if it is unintuitive. To not do so is to be railroaded.

And it's that last part in particular that identifies the most fertile candidates for a good conspiracy theory. Like, is the Earth round? It looks flat to me. Essentially all evidence you can throw at the notion falls either into at least one of, "I witnessed it, trust me bro", "hope you like letters in your math equations" (people who can't intuit math won't be impressed by any proofs), or "you can do this experiment at home, you just need / so you can watch for ". A depressing sum of people in the world will remain unconvinced by any demonstration that isn't simple, intuitive, and of an overwhelmingly obvious magnitude. Complex answers or answers that observe tiny effects are scams.

And just like that, we've abandoned rational thought and replaced it with trust-averse thought. We've invented the notion that the world is a hostile place where anyone trying to hand you something is an agenda-pusher trying to extract something of value from you. All of the world's major institutions are shams designed to keep you complacent in some sort of world order that is merely using you. To participate in it is to further your enslavement.

In that hellish headspace, conspiracy theories almost feel like a haven. Finally! A group of real thinkers who share your frustrations about the world! The underground movement working to free us all from the hostile system!

Except, no. At best it's just a bunch of people who are wrong indulging in a little harmless escapism. At worst it's a mass of people getting Immanuel Goldstien'd by the very kind of well-spoken swindler they're breaking their collective backs bending over to avoid in the first place. Regardless the form it takes, my hypothesis remains: proliferation of conspiracy theories is merely a symptom of a lack of trust.