Around the early 1970s, the great watch-word of the culture became "back."
This came primarily in two forms: back to nature (left), and back to the Bible (right). Under the hood both embrace the naturalistic fallacy (natural equals good) and the idea that there is a proper order from which we have deviated (sin, redemption, reconciliation). This manifested as the Religious Right, the anti-development wing of the Green movement, dogmatic Skepticism (a.k.a. scholasticism), and finally the alt-right.
The alt-right is the ultimate Hegelian synthesis. I'll get to more on what I think is happening today later.
IMHO this was driven by a number of things. These are some that jump out at me:
"Duck and cover"-- this was the generation that grew up with the looming terror of instant thermonuclear annihilation. A bit of ludditeism and retro fantasy is understandable.
Social and urban decay-- by the 1970s pollution was very bad in the West and cities were becoming vast ugly slums. Families were falling apart. Crime rates were rising. Reality did not look so good. See also: duck and cover.
Disillusionment with the collapse of the optimistic and futurist 1960s psychedelic counterculture. By the 1970s the Human Be-In type stuff had given way to Altamont and Manson and "acid casualties."
This was the generation that grew up on television. Broadcast TV is the most passive form of media in history and encourages escape into fictional idealized worlds.
Finally I think we got overwhelmed on an emotional level by rapid change and rapid discovery. Years ago I was thinking about this topic and came across a photo of the Earth from the Moon. I saw it through different eyes, saw it not as an amazing picture of accomplishment but as a terrifying image of our "frightful place in the universe" as H.P. Lovecraft so eloquently put it. Look at that picture. Do you see a God who cares about us? Do you see anything that will save us? I just see a speck of dust covered with a thin film of air floating in infinite black mystery. If an asteroid came along and whacked that speck of dust, nothing would care.
There were many other things too, like the de-funding of basic research in favor of "practical" research, but I see those as secondary effects rather than primary drivers. The primary drivers are deep philosophical and emotional currents.
Capitalism kept driving innovation, but not invention. We kept taking the stuff we'd invented in the first 2/3 of the 20th century and refining it. We took microprocessors from toys to today's behemoths and we took feature sizes down to <10nm. We made cars safer, faster, and more efficient. We cleaned up the air and the water (at least in the West). We incrementally improved health care.
But we stopped inventing. I think invention requires a fundamentally progressive worldview. To invent is to posit that there is a better way that has never existed, which negates the possibility that there is or was a better way today or in the past. Invention is fundamentally anti-tradition, anti-nature, anti-status-quo, and imaginative.
It goes without saying that if you accept the naturalistic fallacy (or the theistic version) or a dogmatic and scholastic approach to knowledge there is no point in inventing. Invention is either a sin, foolish, or futile.
Fast-forward to today:
I think it's ending. If I had to put a date on it, I'd say the day SpaceX landed its first rocket. Seems a good enough piece of symbolism to me.
One of the symptoms of its end is a final blow-out phase. The alt-right, as I said above, represents a total synthesis of the retro-left and the retro-right. It combines concrete manifestations of the luddite left (anti-tech, anti-GMO, anti-health-care, anti-vax, etc.) with concrete manifestations of both the religious and secular reactionary right. As such it has swept up both 70s-liberals and 70s-conseratives. Under the hood it is driven by explicitly reactionary traditionalist thought, including but not limited to the likes of Julius Evola.
The alt-right's embrace of racism and sexism also represents a final total embrace of the naturalistic fallacy. The idea of global human equality is profoundly unnatural. Racism is natural. Gender inequality is natural.
It's true that the alt-right is partly a millennial thing, but it's being driven by boomers and late-boomers.
My prediction is that the alt-right will flame out spectacularly and then the 70s will finally be over.
https://www.youtube.com/watch?v=dNMhl7YuKEY
Edit: Thiel's backing of Trump and the alt-right is why I doubt I agree with him about the causes here. Either that or he's playing insanely "meta" 5D-chess and is actually trying to accelerate the demise of the zeitgeist by driving it to its final culmination. That would be true high magic, but I doubt it.
Edit #2: our frightful place in the universe: https://www.nasa.gov/sites/default/files/moon_and_earth_lroe...