He's tired of the cycles, of all the people being sacrificed, and of their artificially extended lifespans. He wants to set us all free to return to our homes, and stop this place from pulling more and more people in to keep the cycles going.
This part of the caves is called the South Block. It's where they send the groups they're giving up on. There's still games, still wins, but at any moment they could stop entirely... King's already planning to bring a new group into the North Block, to start it all over again.