My head cannon is it’s because lemmy.world and lemmy.ml are tankie echo chambers trying to be the “default” instances. Lots of people aren’t down with simping for authoritarian regimes.
Other than that your reason may be most likely. Just people being unhinged. I doubt it’s Reddit revenge though, Reddit hate seems to be pretty universal; even among people still using it.
Could have fooled me. Maybe it’s not as extreme as the others but the creators are still rumored to be tankies. It’s entirely possible that I’m wrong though.
I did see a comment in the politics community get tons of downvotes for saying something unpopular. A mod replied saying people were also reporting it but they’re allowing it to stay because it didn’t break any rules. I checked back later out of curiosity and sure enough it was removed.
Just to be fair to lemmy.world however it’s possible some mods are acting in good faith like the one that replied while others don’t have the same standards.
PSA: The fediverse doesn't work when everyone's on one instance. If you haven't signed up yet, pick a smaller instance! Choose one from the top 30 or so and you'll be golden. Less server issues and less instance drama (like beehaw defederating from .world).