I believe bona fide socialists started taking over colleges in central Europe in the late 1800s and it just started spreading from there, to Britain, to the States, etc. over the course of the 1900s. Through the universities, they could indoctrinate young professionals and groom them into furthering the cause.

I think that the university system as a whole is built by socialists to produce more socialists. There are colleges that aren't, of course. But definitely all the Ivy League and every publicly funded university.