At its core, a conspiracy theory is an exercise in the creation of modern mythology. So are urban myths to some extent, but with conspiracy theories, you can see how the narrative becomes increasingly intricate and eventually finds ways to connect with other conspiracy theories to become a part of a larger narrative. When our ancestors created their own mythologies sitting around the fireplace and exchanging stories, this was more or less the kind of dynamic they were engaged in.
So when we see these things emerge and become more and more elaborate, what we're really seeing is collective fiction creation at work. There are forums dedicated to actual collective fiction creation, of course, but that's a self-conscious version of this process. Conspiracy theories are much more organic.
That's why they can be so dangerous. Everyone who contributes to a theory, whether by retelling or adding a piece of flourish somewhere in it, gets invested in the thruthfulness of the narrative. In that sense (and I mean this with no intention of disprespect whatsoever), it is a miniature form of how religions come to being; from their inception to their maturation. What fundamentally separates conspiracy theories from becoming a real religion (thus far) is that they don't have the benefit of thousands of years behind them and the chance to develop a full-blown cosmology. There is also the lack of mysticism that religions (and religious cults) have because their subject matter is not all that conducive to branch into that direction. Cults have leaders who can manipulate the belief by doing things like connecting UFOs to angels or something divine, but that's a connection that's harder to make without an external push. But maybe with enough retelling ... who knows?
And that's where thing can get dangerous, obviously. Back in the day, people were shy about their conspiracy theories. They harbored them, of course, but they could not go too far into them if they were interested in maintaining social credibility, so they kept it to themselves. There were indeed methods for exchanging these stories but creating and distributing zines were laborious, which slowed that process down (JFK conspiracies managed to get quite elaborate though). Needless to sat, the internet changed that. It also made sure that this fascinating exercise in human creativity and instinct for storytelling, became weaponized into a tool of tribal identification and rationale, like almost everything else these days.
Well, that's humans in a nutshell. Our best qualities can turn into our downfall in the blink of an eye. We all live in a Greek tragedy, after all.
[end public musing]