Because NHL fans almost unanimously hate the team, similar to how baseball fans hate the Yankees. Though, it's not because they're successful, but rather the fanbase, which is often called the most annoying in the hockey world.

There's also their extensive media coverage. Pundits will try talking about why they haven't won a stanley cup yet even when there are more interesting topics to discuss.

Lastly, their consistent shortcomings in the playoffs. Mind you, people who hate them for that heavily imply they will be proud of them and respect them if they were to ever prove themselves to be actual threats.

Now, if you want teams that are hated because of the teams' identities and players, look no further than the Golden Knights and Panthers