Flat earth started from YouTube recommendations. They had a whole non-annonymous conference where they were happy to talk to the guy from All Gas No Brakes on camera.
https://www.youtube.com/watch?v=H110vCGvTmM
Pizzagate and QAnon started because many people understand something is fucked up but lack the correct tools to understand the systemic problems of society (of which you and I would probably disagree as I blame capitalism and imperialism) so they invent conspiracies to explain the world around them. In many cases, their conservative, libertarian, or liberal ideology does not permit them to critique the systems around them, so they must find some other way to explain the situation, which revolves around (non-system challenging) elite conspiracies. It's difficult to disabuse people of the fake conspiracies because real conspiracies against the public are routine. Some are boring (such as the SV conspiracy to depress software engineer wages). Some are exciting, such as what the CIA is publicly documented to have done overseas by selling cocaine to fund their black operations in the Iran-Contra scandal.
Also, there was a kernel of truth to Pizzagate and QAnon. Look at the Clinton's relationship to Jeffery Epstein. However, the right was unable to metabolize real existing issues and started fantasizing about a fascist coup executed by the president (whom they say rejected Epstein after he found out what he was up to... but didn't do anything about it). They make up concepts like he's tagging and bagging hollywood celebrities and subjecting them to military tribunals but replaced them with clones.
You can't beat a political problem with a technocratic solution, especially one that is proven not to work and that harms real people.