Which isn’t crazy if you strip it of its politics and just consider the lifestyle itself.
Many people latch onto what are effectively caveman diets (especially that). And other people justify doing whatever “weird” stuff by saying that it works similar to how we used to do things, like defecating in a squat position instead of sitting on a throne. And indeed, some of the biomechanics are corroborated by findings that tell us that “sitting is the new smoking”.
Then you have the deluge of news about how you literally can’t do anything, ever, in modern society (lightning, food, air quality) without giving yourself X and Y (bad stuff).
That “caveman” philosophy is basically the most conservative approach to living that exists; better the evil you know than the evil you don’t (modern society changing all the time; see for example smart phones which are quite new).
Of course, the caveat to the above paragraph is that we don’t truly know how to “caveman” since we didn’t grow up like that. So it’s not strictly true that it is an uber-conservative approach.
Where anarcho-primitivism fails is that we’re seven billion people on this earth, way too many to go back to hunting deer and rabbits and whatever. The Unabomber figured out that he couldn’t simply make the individualistic choice (see: liberalism) of going out into the woods and start living by himself, because the found out that Civilization would encroach on him. And what’s a hermit got to say to the federal government giving him an Eminent Domain claim or whatever it’s called?
And then he took it in a bad political direction.