Conor McGregor? Okay, so hockey is a certain kind of a sport. The other players can make dirty, ratty plays on you. Slewfoot, cheap shots, head shots, flying elbows. Additionally, if you actually are a star player, you might focus on being a star player. There are face punchers in hockey, but few can actually play hockey at a high level, as well. McGregor's thing is fighting, so he can stand his ground, indeed. But if his thing was hockey instead, would he act like that?
The biggest difference in reality is that combat sports are all about PROMOTION PROMOTION PROMOTION. Sure if you got two great fighters, the fight promotes itself, but you know what promotes it even more? When the fighters are trash-talking and saying things in the public about one another. Suddenly, that builds up your brand, and then when you can back it up, it builds your brand even more. Muhammad Ali was a famous trash talker who would say all sorts of things before fights.
For someone like MacGregor, it's a mixture of both who he is, and a marketing strategy which draws more attention and thus raises the demands that he is able to extract, and has contributed to making him fabulously wealthy.
In leagues like the NHL, NBA, EPL, etc. your value is going to be primarily extracted from how well you contribute to winning. If you are being a distraction disproportionate to your impact on winning, teams don't want you anymore.
For instance, despite being ++ defensive player, the Memphis Grizzlies told Dillon Brooks after the season that under no circumstances will they be bringing him back, because all of his feuds and trash-talk were garnering too much negative attention. If he were a Boxer or MMA Fighter, all that stuff would promote his brand and raise hype for his fights, either to see if he could back it up or get his ass kicked. If he gets his ass kicked, well, that's basically the end of him getting attention, but if he can back it up and win, he will keep doing it and keep gaining attention. That's basically MacGregor's career.
Someone like Draymond Green has been a bit of a mix of that, insofar as he trash talks a lot, does a lot of things to garner attention in a not always positive way, but he has massively contributed to winning and been a vital cog to the Warriors dynasty. So he's been able to get away with it. At the same time, he doesn't make a higher salary because of it, he gets paid based on how much he contributes to winning, not the expected PPV subscriptions for his events. When he punches a teammate, it becomes a debate on to what extent he is "worth it", but if the Warriors feel he still contributes to competing for championships, they keep him around for that and just deal with the other stuff.