Because they have 16 graduating starters and are only returning 6 projected starters. Therefore, the overwhelming majority of their Rev Share + NIL money is being freed up. By comparison, ND is returning 15 starters (16 if Onye gets a waiver) and a slew of guys like Otting, Absher, Ausberry, Sneed and Talich, that they had to pay good money so that they would be willing to stay and play in rotation.
This isn't a difficult concept. It's no different than professional free agency. If team A has $100 million coming off their "cap" because of expiring contracts, you now have that money to spend on the free agency market. If team B has $20 million coming off their "cap" because their contracts aren't, expiring, they're going to have substantially less money to spend than team A does.