Leach spent much of his life growing up and coaching in towns with populations less than 50,000 so going to a place like Starkville was returning to his roots in some respect. He had a 10-12 year stretch where he coached at Ky, OU, and Tech and those were the "big" cities that he lived in during his life.
Additionally, when you cut your teeth coaching at places like Cal -Poly, College of the Desert, Iowa Wesleyan, in Finland, and Wazzu you have been fighting with a short stick in terms of resources and facilities so again I doubt he saw the challenges in Starkville most every other coach would see when looking at that job.
If you are Sark, Sitting at Bama, anything you need at your disposal, you can get into any recruits living room in the country, you already know how damn tough it is to be a head coach, do you really consider that job?
Truthfully, I foresee a time in the future whenever that might be when we start to see the consolidation AND reduction in the top tier of college football when the network people are sitting around with the conference reps and ask "Do we really need to include 2 schools from Mississippi ( and or Indiana etc.....)?" A conference rep will speak up and say something about tradition etc., to which the network people will laugh and correctly point out that the conferences sold out the idea of tradition a very long time ago and the only discussion is who is kept and who is culled.