I've heard the Knute Rockne (also heard that's why Ara Parseghian) reason, the Kim Dunbar/NCAA investigation reason, and health (neck, wife's cancer) reasons before, but never the 10 player exception as the reason he left. If he still wanted to coach why didn't he somewhere else immediately. There had to be plenty of suitors including the MN Vikings.
Notre Dame has so many advantages that I doubt a top coach avoids them. They have NBC, play a national (international this year) schedule in that they strategically play games all over the country - west coast, mid-west, NE, and south, hundreds of top Catholic school players want to go there (look at CD-H), BCS bowl and revenue tie in, and a great/ well-known history.