In the NFL there are only 32 teams, and 12 of them make the playoffs (~38%). In the NCAA there are 130 FBS teams and 4 of them make the playoffs (~3%).

So in the NFL it's often going to be a rematch, if not during the championship then at least during the playoff, and it's okay because every single team has exactly the same opportunity to make the playoff. I don't mind when a 9-7 Arizona team wins their terrible division and then wins a couple games to make the Super Bowl, because there was no "eye test" to determine that they got their spot. Nobody sat in a room and said "sure, Arizona's 9-7, but they lost a couple of their games close, and they had a tough schedule, and they have the best coach in the league, so we're letting them in over the 9-7 Bucs because we feel like it." In the NFL rematches are part of the game, they happen every single playoff, and nobody cares because the system is set up to reward the best team, not the one with the biggest name.

In college football Alabama gets breaks for no good reason, but just because we feel like giving them to them. If Vanderbilt had played the exact same schedule and won in the exact same manner with the exact same scores, they'd be playing in the Capital One bowl. I wouldn't even have expected to see them in a NY6 bowl, but they might have a chance at one. But because it's Alabama and the committee believes they're the best, they put them in the playoff despite not having earned it on the field. If OSU had played Bama's schedule, OSU would be in the playoff right now. Same for USC.