I think it was a manufactured bestseller. Selling books is a for-profit exercise. I don't think crazy theories are anything new, "new age" beliefs are really a continuous thing since the second great awakening at least. But in the 70s, bookstore chains realized that a certain demographic bought a lot of books, and you no longer could leave all that profit to ill-run independent crystal-selling bookstores just because of some high-minded concern for truth. Give the voracious book buyers the books they want, let the marketplace sort out what's true or not. That was the ethos of the time.

This demographic was called "new age" by the marketers, but almost no one who bought such books called themselves new age.

But people who wrote such books became very aware of the demographic profile too. And while there had certainly been grifter cult leaders before who didn't sincerely believe what they preached, now they realized that they could go straight to profit, just by writing a book. No need for the messy high-intensity "make a cult" step. The bookstores were on their side now.