It is ABSOLUTELY a correct use of the term. Husker fans create a HIGH demand for good football. If we didn't, the University wouldn't dump huge sums of money into facilities and coaches. If the fans didn't care if we won or lost, there wouldn't be a 35 million dollar HC on our sidelines. You clearly haven't thought this through. There are exactly ZERO perennial powerhouses that don't have a rabid fanbase.
Edit: and your claim about being nationally relevant is wrong as well. If you're in the championship game of a Power 5 conference, you're nationally relevant. When you're in it 3 out if 4 years while changing conferences, you're definitely relevant. Unless, of course, the definition of relevant has changed in the last decade.