Granted, when Reagan (and Nixon and Goldwater) came on the scene there was a lot of talk about how the specifics of California (or Western-state) political culture had shaped them, but they wouldn't have had such a resonance in the rest of the country if their appeal was so closely tied to Golden State or Far West specifics.
The Orange County conservatives one heard so much about in those days, weren't closely tied to the big growers elsewhere in the state, so far as I know, and Reagan-voters elsewhere in the country had even less to do with California's labor struggles.
Just what "caused" the modern conservative movement is hard to say, but it was the problems of the 1970s -- crime, recession, inflation, the Vietnam defeat and Soviet expansion -- that made conservatism popular enough to get Reagan elected. Liberals see race at the bottom of everything, but concerns about busing or affirmative action didn't always have much to do with the crude racism of earlier years.
The Frankfurt School is a red herring. Political movements look for allies and areas to expand into. Even without obscure German theorists, eventually the left would have looked to feminists and gays, as they did to racial and ethnic minorities, to replace white working class men, who were becoming reconciled to capitalist conditions.
Most leftists now don't have much use for the old dead white Germans who hated jazz and deplored popular culture. The views of those who do claim to admire Adorno or Horkheimer don't have much in common with what those thinkers were saying in their own times.