Two things (well, actually quite a bit more than two, but two particularly relevant things): first, the rise of ultra-curated news input and social media. Time was that all but the most fringe outlets would make at least a token effort towards presenting news in line with reality; you had to go to a great deal of effort to avoid it, and people would be exposed to others who'd socially punish proclamations deviating from it. You couldn't socially OR ideologically isolate yourself like you easily can today. Today, it's very simple to avoid anyone who thinks differently from you and still routinely socially interact with people, which makes it easier and easier to think of any diverging opinion as crazy or evil, since "no one thinks that way", so it's only the crazies.
That's reason one; there's no longer much of a cost to being crazy. But that's the smaller thing.
The big one is the increased revelation that many horrible hidden things ARE, in fact, happening. Remember True Lies, and how ridiculous it seemed that the government would be wasting resources spying on its own citizens without warrants? And then Snowden came along and showed us that not only is it happening, but happening at a scale bigger than anything the conspiracy theorists had imagined? Or how about when Anthony Fauci misused PCR testing (which was never intended as, and is worse than useless as, a diagnostic tool, as per Kary Mullins, who invented it) to diagnose patients with GRID, and push them on to the AZT that wound up killing many of them? And then did basically the same thing on a much larger scale 35 years later, when Mullins was dead and unable to object? Obviously, the Thalidomide shots aren't nearly as lethal, but they went through much, much less long-term safety testing, and anyone calling for even basic medical practice (especially in light of the fact that horizontal gene transfer risks giving us TB or rabies- or, heaven help us, bird flu- with Covid-level contagiousness) got lumped in with those claiming that it was all the work of an evil cabal of "elites" trying to kill or sterilize everyone.
That's the real reason: because the world IS crazier now.
Let's put both aspects together: when I was born, 90% of American mainstream media was controlled by just fifty companies. That may not sound like too few, but remember, that's one per state- and it's NINETY PERCENT. Today, that same 90% is controlled by... six companies. With that kind of consolidation, it's hard to NOT brainwash people.
