I am going to go back to Notre Dame as although I am not sure they fit the term fallen program since they have had some competition, I do think Notre Dame may have fallen the furthest from a prestige standpoint because they once used to be the center of College Football and it has been a long, long time (longer than Nebraska) since their high point.
Notre Dame was arguably, the center of the College Football world from 1930s until about 1980s. Lou Holtz era seems to be their last big hoorah.
Notre Dame has some shot to get back but I think staying independent is holding them back. I am also going to get to how Miami's fate may match Notre Dame's decision.
Notre Dame needs to join a conference, in my opinion, to get back. They have only two realistic options: ACC and B1G. I think if Notre Dame joins the B1G, they will be in the shadow of Michigan and Ohio State. They will make a lot of $$$ but I don't think they would win.
If Notre Dame joins the ACC, they will be the center of attention with that league along with Clemson (if they continue to maintain their high level). The ACC looks like a conference ready to implode but it has a lot of good programs that are underperforming.
If you look at it, the ACC can boast several programs with some history of College Football success including:
1. Miami
2. Clemson
3. FSU
4. Virginia
5. Virginia Tech
6. Pittsburgh
7. Syracuse
8. NC State
9. Georgia Tech
10. Louisville
11. North Carolina
All the programs listed above have potential. Notre Dame could come into the ACC and rejuvenate its program along with some of the ones on this list by the added $$$ of the deal. Bring another team, perhaps West Virginia, along and it just makes sense. You shore up the ACC and you have a league that includes media markets such as Boston, Atlanta, Miami, New York, Washington DC, etc. The entire Eastern Seaboard basically. You also have recruiting access to the Carolinas, Pennsylvania, Florida, and Georgia to bolster your teams.
There is great untapped potential with the ACC.
Financially, Notre Dame to B1G makes sense but from a program building aspect, Notre Dame would see more success in the ACC.
I think Miami's fate is based on the survival of the ACC. They are not as attractive of an option as Clemson, FSU, UNC, etc. to B1G and SEC. If the ACC can survive and shore things up with Notre Dame, Miami would get an influx of capital and with the right coach could be rolling again at some point.