They are always gonna stick to the rules even if VAR isn't around ... the ref sees the ball enter the net, but he's also seen two fouls just before it did, one from each side, so even though he may initially have handed Haaland the advantage, he then sees the Liverpool player pushed to the floor by Haaland, possibly denying him the chance to clear it .... so he was never gonna give the goal.
The Liverpool player was red carded for trying to stop Haaland in the first place, and denying him a clear goal scoring opportunity, even though the ball still ended up in the net lol!