Very simple. The marxists found that class division did not work well in the USA because of upward mobility so they turned their division tactics to race in a second effort. The professors teaching this are marxists too, or they are forced to teach it to keep their jobs.
Yep.
Cultural Marxists divide us by class/income, sex, age, philosophy/religion, party, and more strongly now, by race.
Divide and conquer, an old old tactic.