There is always more to these investigations than we know about. There were 154 pages after all - have you read all of it?
I know the father of a guy who is an attorney for the NCAA or at least he was. He investigated USC after Pete did his nice work there among others. The guy didn't talk in specifics but did say they spent a bunch more time and uncovered many more things than were actually thought to have happened. It wasn't like they did this with one or two people either, it was a pretty big team. They operate on facts and evidence so just saying something happened, doesn't make it so. There has to be proof, unlike what I see on this site - if someone thinks it is true, then it is. He also said that they often find one coach doing something the head coach knows nothing about, I can easily see that happening. Why risk letting more people know what you are doing.
I won't pass judgement on the penalty as I don't know what they did actually find as problems - it didn't appear there was mass payment to recruits - at least that was found out. I also don't know all of the penalties. There could be a ton of internal triggers and follow-ups that go with all of this which I would assume would be at least the case. Losing scholarships is substantial. I know it would hurt us but maybe not in the years we couldn't give them all away.
The guy also said they all know what happened at SMU and that place never recovered so yes there is an awareness that when you bring the big hammer down, it is a big one for a long time. I also don't want to live in a glass house on all of this.