I have noticed it in a targetted fashion against certain games, especially when they are threats to large game franchises that make a lot of money.

For example one of my favorite games Operation Harsh Doorstop is quite regularly review bombed, ultimately I don't see how people would be so consistently motivated to review bomb the game, attack the developer and attempt to spread drama on the discussion forum unless they are paid. I am not exaggerating, this is an entirely free moddable game (hence why it can be review bombed easier I guess) and it really makes no sense how vile some people are in the reviews. Sure the game is in early access, it has lots of rough edges but the core game is just fun... the way people talk about it in the reviews is truly mindboggling and I have played A LOT of games so I am not just being biased here because I like the game.

I can only conclude that there is a lot of money in multiplayer FPS games and the owners of IP like Battlefield, Arma, Squad and live-service trash games like Enlisted REALLY don't want there to be a fun, free moddable alternative to their shit offerings.

https://store.steampowered.com/app/736590/Operation_Harsh_Doorstop/