What expansion do you mean? This is the first time there has been an actual expansion proposal for the CFP. If you mean conference expansion, there is a big difference.
Regarding the playoffs, there is definitely more money in it for the networks. CFP games bring in significantly higher ratings than regular season games. Even if the added playoff games only bring in half the ratings of the semi finals, that's still much more than the average regular season game, or bowls.
Ratings didn't have anything to do with Ohio St. jumping Penn St. in 2016. Penn St. had 2 losses in 2016, as opposed to 1 loss for Ohio St. The very next year, Ohio St. had 2 losses and was jumped by 1 loss Alabama.
I'm not saying I agree with it, but the losses were the deciding factor in both cases.