I went back some time ago and pulled up top 25 rankings from random years, going back to 50s or 60s. What you saw was basically a rotation of the same teams. Every so often you get a Northwestern or Colorado blip for a year or two, but you essentially had the same teams cycling in and out.
Success breeds success. Before the NCAA put the scholarship limits on programs in the late '70s top teams would recruit and sign top players just so their rivals wouldn't have them. Bear Bryant was famous for this, having 120+ players on scholarship to keep them away from Tennessee, UGA, Auburn, etc.. It really was a rich get richer world back then. Miami cheated their way to prosperity and so did Auburn and Clemson. USC and UCLA used integration of their teams to climb to the top of the heap when the Southern teams wouldn't have black players and Notre Dame was dominant because they didn't have to recruit, they simply "gathered" Catholic players.
I don't think Carolina is going to be dominant any time soon, probably not in my lifetime, but they can be relevant. However, as long as the fans and the admin are accepting, not satisfied or happy with but accepting of 6 or 7 win seasons, that is what Carolina is going to be and 6-7 win teams aren't relevant.