In 1997, Michigan's Charles Woodson won the Heisman Trophy and Michigan won the national title. It was shown several years later, in 2001, that prior to and during his Heisman year at Michigan, 1997, Woodson took money and other benefits from Summit Management, a sports agency. Auburn's All-American Victor Riley was also shown to have taken cash, and a third player, also from Auburn, running back Stephen Davis, admitted in an interview that he took cash from Summit while at Auburn.
NCAA spokeswoman at the time Jane Jankowski said that accepting such benefits while competing would violate NCAA rules, but that the NCAA typically does not investigate such cases after the player has left the school unless there is blatant evidence that university officials knew, or should have known, about the violations. "We don't see any evidence of that" Jankowski said. Jankowski also said the NCAA would have no power to revoke Woodson's Heisman Trophy.
So first of all, apparently Auburn is on the 'favored list' as well, because I don't recall seeing any Auburn games forfeited due to the actions of these two players. Secondly, if USC didn't have any involvement or knowledge of Bush's step-father's shenanigans, this is a pretty close parallel to the Woodson case. Michigan still has their wins and their title, Woodson still has his trophy.
Well with Alabama a much more minor incident happened (the Langhaman incident detailed above) and that ended up costing them about 20 scholarships and 10 games of forfeits. That was the first time that Alabama was ever on probatation.
But your larger point stands, historically the NCAA doesn't care about cases like this unless they have a bone to pick with the team involved. For whatever reason, the NCAA wanted to hammer Alabama and they seized on the first thing they could.
Right now, the NCAA has no problem with USC and they are probably the 2nd most profitable team right now behind ND so they won't be touched.
To be clear, I don't think that USC knew directly what has going on, but they also made it their business not to know. That is how all schools do it. I don't blame them a bit.
The problem is that it is like the 55 mph speed limit. It makes everyone a violator and the NCAA can pick and choose who to hammer.