That's a good question, but if you think back to sci-fi movies of the late sixties and early seventies, movies would often have a left winger as a villian. In Soylent Green, the villans took bodies and made food for an "overpopulated" Earth. A recent James Bond film, Quantum of Solace, had an Al Gore clone as the villain. Even the recent Marvel villian Thanos was left wing.
Perhaps they know that after a while, the evilness of the protagonist will be forgotten, but an imprint of the movie "ruling class hunts deplorables" stays.
It wouldn't' surprise me if Thanos was the true inspiration for the incel puke who shot up El Paso.