I've thought a lot about this myself. I think the coasts are more progressive because they are the entry points for the rest of the world; there's more diverse exchange culturally for that reason. But, I wonder too if it's the population sparseness of the Midwest itself, i.e. because it's so spread out? Perhaps that sparsity between the Appalachians and the Rockies allows enclaves of intransigence to flourish. After all, the Midwest became the retreat where people fled from the increasing progress of the East and West Coasts. It's the region to where folks who didn't want integration fled – they actively sought out white spaces. In those enclaves, they were able to raise increasingly ideologically white generations, and to resist the progress of the rest of the world.

The Ozarks aren't real mountains https://www.newworldencyclopedia.org/entry/The_Ozarks