Late 19th century . . .
Leftists figure out that “the workers” are not going to revolt, because capitalism is making their lives better.
That’s okay—a revolutionary vanguard of intellectuals can do it for them!

Early-middle 20th century . . .
Leftists figure out that that doesn’t work either.
Never mind the whole worker-vs.-capitalist thing. We’ll switch it to “oppressed” vs. “oppressor.”

Mid-20th century . . .
Leftists figure out that, while not perfect, things aren’t too bad for so-called “oppressed” people either, and they too have no interest in revolting.
They’re not angry enough! We must “raise their consciousness,” stir up resentment, and “rub raw the sores of discontent”!

Leftists are like those deadly automated planetary defense systems in sci-fi stories, still operational and killing people centuries after the war they were designed for is over.

Just stop, lefties. Stop making everyone unhappy.