I don't follow sports much beyond the headlines, but what have the other leagues done?
The NBA commentators commented on this calling out the NFL. It's part of the NBA genetics for players to be politically active and as a team and as individuals make political statements on the court. It's why you don't hear it much because it's just part of what the league does. How far this goes back with the NBA, that I can't say. But at least now the NBA is considered a 'player's league' where players have greater power and autonomy than before, and political and social activism is very much a part of the NBA.
Besides the NFL, as much as I enjoy watching the sports from time to time, is a fundamentally stupid game, in that I mean, the repeated concussions these players get over time will make them stupid or some other brain damage symptoms.
One thing to note is that I believe the NBA has a “must stand” policy already so it’s unclear what would happen if that was tested. My guess is amicably given the NBA already let’s players and coaches speak out as much as they want.