In addition to what others have said, I think a lot of people in Hollywood are leftwing, but lack theory. They're trying to disseminate leftwing ideas, but don't realize how entryism doesn't work. They will tiptoe around execs (who are mostly a bunch incompetent of failsons with zero media literacy) to get projects made.

One of the examples that comes to mind was Dalton Trumbo, an openly communist writer who was blacklisted during McCarthy. But he had a lot of friends in Hollywood who liked working with him, so they helped him by giving him a pseudonym on projects or coming to his defense in court.

Stanley Kubrick would help Trumbo get back in the open with Spartacus, starring Kirk Douglas. It's not like Douglas became a tankie Maoist, but he did have positive things to say about Trumbo and his writing. Douglas' son is Michael Douglas, married to Catherine Zeta Jones. Again, they aren't die-hard communists, but they at least have enough connection to a leftist to have some leftwing ideas.

tl;dr-- there used to be a bunch of commies in Hollywood until McCarthyism, but some of the sentiment is still present because LA is a small town.