There are certain ideas that are highly seductive, so much so that even “WEIRDOS” occasionally dabble in conspiracy theories. So why weren’t conspiracy theories a bigger part of life in the late 20th century? I believe this is because the media was almost completely controlled by WEIRD people. The news desks at ABC/NBC/CBS stuck to the mainstream version of events, unless they had clear evidence that the official were lying (say after the Ellsberg Papers came out.) So there was no major institution to form and disseminate conspiracy theories. These theories did exist back then, but never gained enough traction to have a big impact on society.
The internet changed everything. More specifically, it democratized information sharing all over the world. There are no more “gatekeepers”. Because less that 10% of the world’s population is truly WEIRD, the internet has made conspiracy theories the dominant epistemic style of the 21st century. Just as the 21st century will be a low interest rate/high asset price century (as I predicted years ago), it will also be a century of widespread conspiracy theories. I doubt whether I’ll live along enough to see another president who is generally accepted as legitimate.
That is from Scott Sumner, there is more at the link.