“If that’s so, why are Arkansas, Mississippi, Louisiana, and Kentucky among the poorest states in the union?”
Never fully recovered from what the North did to them.
There are poor blue states and poor red states. There are wealthy (for now) blue states, and wealthy red states. Amazingly enough, Charles Murray might have more answers for this conundrum* than the usual political scientists.
*Base on his study of what we call “human diversity.”