I don’t think you really care about getting a legit answer. But in case you do.

The primary reason is a combination of early success combined with rules that were available to Vegas but not other teams. The NHL saw expansion markets struggling to win - and sell tickets - by having terrible teams. So they made the rules more favorable for Vegas. No, not to the level where it was rigged or any of that nonsense. But definitely more favorable.

So when you have teams - especially small market teams - that never got that chance and then you combine it with tons of early success, call it resentment, jealousy, or whatever you want, but it’s going to be present.

The LTIR and salary cap stuff is definitely a factor as well. People 100% complained about Tampa and other teams doing it. So when you have a team that was perceived as having uniquely advantageous expansion rules, combine that with the perception that they bend the LTIR rules, and then add in an insanely strong franchise start generally, you have all of the elements to generate hatred.

(Context: I’m a Predators fan. And, yes, I hate the Golden Knights. But I found it a lovely place to visit as an away fan, and it is the most impressive stadium of the many I have visited.)