I think you’re really hung up on that they brought up that Columbus was a shitty person. The joke isn’t even about that. Like you said, it’s well known, it’s the context in which the information is being given that makes it funny.

I don’t know if you’ve ever seen Scrubs, but there’s a scene when a character burst into the scene singing “It’s a Beautiful Morning.” Turns out he’s at a funeral. That isn’t funny because the character sang a song, it’s funny because of where he was singing it and how it’s juxtaposed with where he was. What you’re doing right now is, “so what’s the joke? That it’s a beautiful morning? We already know that! This is woke bullshit!”