So AFAIK it's been a gradual process over the past 50 years. No one particular year or even decade stands out as "The One Where It All Went Into The Toilet".
This was the eruption into the open of the Decadence of Western Civilization in America.
Civilizations fall because of internal moral rot and decay. The counter-culture movement was the eruption into the open of the moral rot and decay that had been festering in America.
Its battle cries were "If it feels good, do it!" and "Sex, drugs, and rock-and-roll!"
Its proponents claimed a "new morality," which was nothing more than immorality, and other virtues that were dubious at best.
In fact, it stood for nothing more than the self-indulgence of the "entitled," "anointed," spoiled children of the men and women who had built the USA from an untamed wilderness, suffered through World War I and the Great Depression, and saved the world from the horrors of naziism and the Japanese Empire in World War II, sashaying down the staircase of civilization in their "velvet slippers."
They were the typical "entitled," "anointed," spoiled, self-indulgent children of rich parents everywhere and for all time, but in large numbers, on a national level.
Maybe this is what decadence is: When the number of "entitled," "anointed," spoiled children of rich parents reaches a critical mass, decadence ensues, and, if it is not reversed, the nation is doomed.
Today these people have commandeered the entire Democrat Party.
In 1968 I became friends with a girl who was a foster child with her brother and sister, their foster mother received $850 a month! That was a lot of money back then.
So many people moved to CA for the great welfare benefits.
“So AFAIK it’s been a gradual process over the past 50 years. “
Much earlier, when the communists moved from NYC to settle Hollywood.
That's my take on it - the frog in cold/tepid/warm/hot/boiling water thingy.
Moved there in 1967, lived 20 years in the Oceanside area. At first it was GREAT, then Reagan instituted state withholding taxes and in three years my taxes , not my wage, had increased 50%. Then the housing boom started and it seemed that my mtg escrow was going up $50 every six months for taxes, no tax deduction for IRAs, then the auto tags inched up, froze instead of dropping one year, then started inching up again. New restrictive regulations on EVERYTHING, especially gun ownership, every year.
Drip, drip, drip. Then one day in '88 I had enough of the regulatory and taxation walls closing in, bailed that year and never looked back.