But neither Saban nor Meyer were thrown into the fire right off the bat when they were finally given head coaching jobs. Saban got his first chance at Toledo and then MSU at a time when MSU had been down for 5+ years and wasn't a high-pressure job. Meyer got his first HC gig at Bowling Green St. and then went onto another low pressure situation at Utah.
Giving a young assistant coach his first HC job at an extremely high-pressure institution like ND is like asking a rookie pitcher to make his MLB debut in game 7 of the World Series. No one would be shocked when that pitcher gets lit up, and no one would be shocked if Sanford crumbled under the bright lights at ND regardless of his ultimate potential several years down the road. Kliff Kingsbury, Mark Helfrich, and Lane Kiffin were all once the "it" young-up-and-comer assistants when they got their first HC gigs and they all struggled (although Helfrich did make the CFP his first year after Chip Kelly left for the NFL). Tom Herman is doing well but he's making his mark at Houston which isn't a high pressure job. There's no guarantee that Sanford would struggle but, given the history of other assistants thrown into high profile HC jobs, it is more likely than not.
Also, the current recruiting class has stayed solid even with the team about to go 4-8 and a coach who is currently on the hot seat. If BK were to go we wouldn't need a blockbuster hire to keep the current class intact, and even if the class were to fall apart, which is unlikely, that's only 1 recruiting class and that doesn't guarantee we will struggle for 3 years. Jim Harbaugh's first recruiting class was ranked 37 (247sports composite). That one bad recruiting year hasn't seemed to hurt him.
