I don't know about "little known", I thought it was pretty common knowledge actually.
But I would argue that at the time period in which he lived, the "lab results hadn't come back yet" (so to speak) on Communism. It was a very attractive concept, at least on paper. Like perpetual electric generators, you had a lot of rational people still trying to figure out a way to make it work.
And if I'm being honest, Joe McCarthy and the HUAC was a dumpster fire of epic proportions.
