If the players' demands sound extreme, that's because the "amateur" college sports model has been entrenched for too long. The boycott threat seems drastic only if you ignore how the courts and lawmakers have protected that exploitative system. The players' movement might seem sudden if you don't see that schools have adopted incremental reforms that favor athletes, while lobbying Congress and fighting in court for athletes to never have full rights as workers.
The Pac-12 players know those institutions won't do the right thing on their own. They realize that direct action is the only path to drastic reforms. They will not shut up and play. Instead, the players are speaking up to say they won't play if their demands are not met.