How long did that period last? It died very fast, and was really only 5 years at maximum. Probably not much longer than the time that covid started until now. A flash in the pan.
1960s is only 10 years so if something went on in the public mind day on and day off for 5 years (like COVID did for 3 years), I think it's a good candidate for the decade-defining theme
There’s a related occurrence of the same principle — we have had movies/stories about the wild west for longer than the archetype frontier period existed.
The lingering effects might very well last longer than the actual event itself though. Hell, the effects of LSD last much much longer than the drug itself lasts in the body. So to me, you're harping on the wrong thing. Sure, maybe the movement lasted a short time, but the mindset is still out there