You really need to dig further than his overall record. He took over a dumpster fire at SMU. They were 1-11 the year before he started.
He's finished 2-10, 5-7, and 7-5. None of that is stellar but it shows improvement every year.
If you've heard of Dabo Sweeney, this is, the guy that saved his job. Dabo was about ready to be run out of Clemson when he hired Morris as OC. Morris recruited and developed Watson. He installed his offensive system at Clemson and it's the one they still use.
He interviewed for a number of jobs the year he left Clemson and was runner up for several posts (i.e. Vandy). Ended up at SMU but probably should have waited another year to leave Clemson because he would have then had some better offers. The Clemson people were in a panic when he left. They promoted assistants that were under him as Co-OCs to have them run his system.
Same thing probably applies now. If he waits another couple of years and gets things rolling at SMU, he'll likely have some better offers come in. He's a gamble but if he hired a good DC and if our fans didn't panic, he'd probably be successful here.
You would have to worry about him being successful and leaving but if that happened, he'd be leaving a successful program and it would be easier to hire a replacement coach.
Let's face it, TN is no longer a dumpster fire. We're a nuclear waste site.