People tend to learn lessons the hard way.
Society is disintegrating in slow motion.
These cities have been dying since the 1950s, certainly beyond recovery in the 1960s. What has been going on since then is a combination of willful ignorance, mau-mauing, raiding the carcass, burning the furniture for firewood, propaganda, marketing, and a con game.
The migration of drug addicts and misfits to the "Summer of Love" in 1967 in San Francisco was made possible because so many companies had already left and so many residents had already departed the city for the suburbs.
Tom Wolfe published 'Radical Chic & Mau-Mauing the Flak Catchers' in 1970.