One more thing that struck me about Kiffin leaving...I think he knows that even with their best team in decades they're still probably not a threat to win the CFP. As a coach you probably know which players would have made a difference on your team. If you look at the closest programs to you, distance wise, you think "If I just had Jimmy J or Bobby Joe" or whoever. He knows LSU and the rest won't stay down forever, he knows he lucked out schedule wise. He probably thinks to himself, this is the best OM is ever going to be, and it was mostly a fluke and we still lost by 10 to UGA. He's not going to say it, but he knows it.
He also knows that just like Mark Stoops, eventually you can't survive with 7-8 win seasons, and then the recruiting gets harder, and then 8 wins turns to 6, and 6 to 5, and then you're fired. It's a cycle few survive. So he knows he has to get to a place where he can always recruit the best players, otherwise he's out of a job in 5 or less.