In the past dozen years or so, the biggest powerhouses to fall from grace, so to speak, have done so for a variety of reasons but most of the time it is self inflicted. Just off the top of my head the steepest falls have been Nebraska, Tennessee, Auburn, and perhaps, Michigan. There are likely others but I assume you mean legit nationally ranked elite factories. Nebraska and Tennessee were bedeviled by some pretty bad coaching hires and neither has the recruiting chops to survive multiple years of chaos the way, say UGA or Alabama can. Auburn is still a formidable football factory but suffers in comparison to the monster created by Saban. Michigan is similar with its nemesis being Ohio State. Some places just seem to, for whatever reason, consistently underachieve relative to their usually glittering recruiting classes. Miami, UNC, and Texas come to mind although the Longhorns did win a fairly recent national championship. It is hard to imagine now but once upon a time schools like Arkansas, Missouri, BYU, and Pitt were seen as being on the cusp of greatness but it was a mirage. For the past 40 years, UCLA has beckoned coaches of promise and has wrecked many a reputation and career. There really are not that many teams in this situation. Far more common, is the plight of the also ran and never do wells of college football. Vanderbilt, Tulane, Boston College, Wake Forest, Duke, Kansas, Illinois, Purdue, Washington State, Oregon State, California, have no chance. None, zero, zilch, nada of ever being much more than punching bags for the factories. We are somewhere in between but another bad year will put us drifting near to a lee shore, too close for comfort. IMHO