The Flat Earth thing makes no sense to me, but regarding Anti-Vax: again, not defending them, but it’s trivially easy to find examples of governments (worldwide) deceptively giving people medicine which had a negative effect on their health, whether as experimentation, sterilization, or otherwise. The fact that vaccines are scientifically known to be safe is just lost in the noise.

I attribute the rise of conspiracy theories to an overabundance of information; doing the research on each individual topic is just overwhelming to the average person and subsequently a simplistic conspiracy theory has appeal.

My pet theory on the flat Earth is that it's been pushed in order to compile lists of extremely gullible people by scraping social media so that these lists can be used later. For what? Who knows. Targets of scams, marketing, propaganda...

Nah, some AI just figured out it was an easy way to get more clicks on YouTube.

I mention flat earth and anti-vax, because they are conspiracy theories that are not obviously driven by the government's behavior.

I am not too familiar with either, but in my view they are definitely associated with ‘authority’ whether then be mainstream media, government, institutions, etc.

Sure, but where I live, these are still held in high regard, yet anti-vax and flat earth spread here too. I don't think the institutions are the direct drivers of conspiracies.

Perhaps I should have made clearer that it was in particular the word "direct" that I was responding too, not the fact that unethical or shady behavior from a government can trigger long-lasting distrust.