He isn't coming here to be just a position coach. He would be coming here as Co-DC. It wouldn't be an empty title either; I would expect him to be significantly involved in strategy and game plans even if he is not himself calling the plays. PK needs help, fucking clearly, and has a history of sharing responsibility and cooperating with his Co-DCs to an extent that most guys cannot tolerate due to ego. It isn't the same as leaving to go work under a lot of other DCs.
We would also probably damn near double his salary. Do not go by what other coaches were making on this staff prior. We have tens of millions in additional revenue coming in from the SEC media deal starting next year and basically all of that is going to be earmarked for the football program (rightfully so). On the flip side Arizona is facing massive debt issues. Even if they could afford to match whatever we offer him they are going to be making major cuts to their football program analyst and support staff. They've already announced all that publicly. Their situation is kind of grim.
Add in the fact that he and Sark are not only close but supposedly 'best friends', with his daughter already at Texas, and you can see how the situation would be appealing.