That was their last lifeline to a “Power” league.
Maybe they calculated the future of that conference was not worth the risk. Is it their calculation that the ACC would lose their anchor schools which would diminish their power status? The ACC would then expand and likely invite the P2 IMO. The P2 probably calculated that at that point it wouldn’t be worth it. Not for them and possibly not for CAL/Stanford. Is that also why they calculated that they’d only need to be a 6-team conference?