If Vandy is personally desirable for him, that's fine. But it is hard to make a case that Vandy is a "desirable" job from a football perspective. Its history of coaching searches and ensuing selections would argue with that.
He is well regarded and well-paid at ND and is the DC for ND. That is a high profile job where he is unlikely to fall off the radar for any length of time. He isn't under any pressure to do the next thing. Taking a bad job just because it is there doesn't make much sense especially when he is a very very good situation at ND. If he isn't happy at ND and is ready to move, that is one thing.
Otherwise, good jobs -- jobs much better than Vandy and that list is long -- pop open all the time. Iowa State, Cincinnati, UCF, to mention a few, all have highly regarded coaches who are going to get better jobs soon. Also, since he already has high level Power 5 experience, when he choses to be Head Coach it doesn't have to be a a Power 5 school. In fact, amid COVID, he might be better served not to move now. While the overall situation should get better, there is no reason to assume that 2021 will be a normal football year.