Cultural Marxism was founded in the Frankfurt schools in Germany before WW2, and because of the Nazis they had to escape to America and teach it in New York's Columbia University. Their teachings are codified in the writings of various Marxist theorists such as Georg Lukács, Antonio Gramsci, Ernst Bloch, Walter Benjamin, and T.W. Adorno to Fredric Jameson and Terry Eagleton. After WW2 some of the scholars went back to Germany and rebuilt the Frankfurt schools and then came up with critical theory.

Sorry to give a history lecture, I just wanted to add to the point how stupid it is to say an ideology doesn't exist even though said ideologies teachings are espoused by the people claiming it doesn't exist.