He's at Washington State because Tennessee idiotically didn't honor the MOU he'd signed to coach here. Other than that, it's because he refused to lie under oath at the direction of his AD at Texas Tech.
As for the rest of your post, he had a top 15 offense and defense in the nation last year at Washington State. Washington State is a worse program historically than Vanderbilt. Texas Tech was just as bad historically as Kentucky/Vandy etc. He got them into the top 10 in the country while there.
He's a great great coach. He lost a guy he'd turned into a great quarterback last year. Replaced him with a grad transfer from East Carolina this year. They are 5-1 with a 3 point loss to USC and are averaging 42 points per game. They've been to 3 straight bowls, went 6-3 twice and 7-2 once in the Pac 10 the last 3 years. Once again, at Washington State, which is, as I said, a worse program than Vanderbilt historically. They were 9-40 in the 4 years before he got there.
Somehow, after all his bumbling Currie hit a 9th inning walk-off homerun. Only there was weird fan interference at the last second and the homerun was ruled an out.
The other sad thing about that is that Mike Leach produces coaches and we missed out on that. His current coaching tree includes West Virgina's head coach, Oklahoma's head coach, Texas Tech's head coach, Central Florida's head coach, and Neal Brown at Troy. Those guys are 27-4 this year combined and 3 of them were ranked in the top 12 this week. Art Briles was also on his coaching tree, he won a whole lot of football games himself. We desperately need a coach that can develop head coaches and Leach does it and does it well.
So basically we hired a completely green/unproven assistant over someone who has rebuilt two of the worst programs in NCAA history and who produces generations of great future coaches. Most likely because, as has been mentioned, he basically doesn't allow the AD to force him into bad situations without standing up for himself.