I've been reflecting of late on science denial and pseudoscience. Obviously there are some recent phenomena that have particularly inspired me, for example the ludicrous RFK Jr. and anti-vax in general, the climate emergency, the resurgence of creationist demands on school boards. These attract overlapping constituencies, hence the phrase crank magnetism, coined by the redoubtable Orac. However, although there is shared susceptibility, I think there are a couple of different underlying causes.
Climate denialism is like tobacco and lead. Denial of the dangers of burning fossil fuels, smoking tobacco, and putting lead into children's bodies were all very well-funded conspiracies by psychopathic rich people who put their already obscene wealth ahead of the health and lives of hundreds of millions of people or, in the case of climate denialism quite possibly the future of civilization. There is no place in hell low enough for them.
However, that does not explain creationism or anti-vax, among some other popular denialisms. (Remember HIV denial? That seems to have faded out.) There aren't any extremely powerful financial interests behind these. But they don't have much in common either. I think there are two different things going on.
Regarding creationism, it was always an uphill struggle for Darwin to replace the Bible. Religion had deeply entrenched cultural power, and it also has psychological appeal that evolution does not, at least to many people, though not to me. Apparently it's just uncomfortable for many to think that humans arrived on the scene by accident, that we're nothing special and the world wasn't made for us. I don't know why the idea of God is comforting to people, if he's good and merciful he obviously isn't powerful, and vice versa. But that's an argument for another day. (It's called the theodicy problem, BTW, and despite libraries full of books trying to solve it, it's impossible.)
But I think something more has happened in the 20th Century, as the physicists' understanding of the universe grew ever deeper, more complicated, and more strange to our intuition. Relativity and quantum theory are not only difficult to understand, but they violate the way our brains have evolved to make sense of the world. There's no denying the technological miracles science has brought us, and it happens to be true that the GPS depends on relativity theory for its precision, and the chips that make our phones and our computers and our cars function depend on quantum theory. However, none of this requires a fortiori that the universe be 13.8 billion years old.* That requires a very long chain of observation and logic. However, if you trust the observations and understand both theories and do the math, it's what you have to conclude.
I think to most people 21st Century physics just seems, to the extent it's comprehensible, absurd, and otherwise just gobbledygook. It's just a lot easier and more comforting to believe the old, simple story they taught you in Sunday school. That doesn't explain the anti-vax movement, however, which I'll get to next.
*Actually there's a newly proposed theory that it's actually quite a bit older, which tries to account for some puzzling observations by the James Webb Space Telescope. But it's definitely not any younger.