Shortest answer: Tribal approval.
The $eminole tribe in Florida $igned off on F$U for $ome rea$on$.
The tribes in North Dakota did not do the same for UND.
1993, 1999, 2013 Nat'l Champion Florida State (ACC) v. 1996, 2006, 2008 Nat'l Champion Florida (SEC) ... annually ...
I'd argue one pushed the other to be better ... or maybe that's the issue.
"Remember when GameDay was in Fargo."
"Yeah, that was awesome. What year was that again?"
"Remember when we had the High Performance Center / Indoor Training Facility ... "
"You mean that building right there?" < points >