There are two 1st round picks on that line in the way of Mason Graham and Kenneth Grant. That, plus they had a deeper reserve of well-developed, quality, and healthy, front seven players. They could rotate in fresh players, and not miss a beat.
As good as Howard Cross has been for us this year, he wasn't 100% for the championship game, and the available reserves weren't nearly as good as what Michigan had. Losing Riley Mills made it even worse. I have all of the respect for Donovan Hinnish, and he's a very capable player, but barring some miraculous development, he'd be more of a priority free agent, instead of a 1st round pick.