It's a little bit like a tiny version of the Mormons if Joseph Smith had read the collected works of Isaac Asimov instead of the Bible and also his name was Yud.

Or to go with less of a sneer, the Rationalist/TESCREAL/Californian Ideology is a loose grouping of fringe beliefs rooted in old-school science/tech fetishism with a lot of science fiction overlays and libertarian/reactionary politics that effectively define "let ultrawealthy tech capitalists do whatever they want" as the only reasonable choice and make it a moral imperative.

Techish (I would use the word techbro here, but that needs an explantion even) people who want to make their fictional science fiction utopia real, but got so scared of their own science fiction ideas going wrong and killing everybody they started a cult around rationality, sort of a Vulcans fan club. They have a pattern where they think they and their methods are smarter and better than actual experts.

When trying to do their own research with an open mind, but they left their minds so open that all kinds of sexists and racists crawled in. Who are welcomed as long as they are verbose enough.

And to close it off, Musk is a fan.

Personally I might try explaining some of the foundational stuff before going into the big R. Scientism, utilitarianism would be my starting points.

ABSOLUTELY CURSED