Old mining and factory towns are extremely sad. When the region stops generating the value that drove its initial growth, the result is an endless downward spiral to widespread poverty. Lots of former workers are unable to make a transition to another job. The only real money left is in the retirement accounts of those who "made it" before the layoffs, and the only jobs available are in the service industry catering to these folks. That money and those jobs eventually fade away. The youngest and most capable workers see the writing on the wall and get out of Dodge. Others hang on as long as they possibly can.
Of course Wal-Mart can't make a profit selling a full-size warehouse full of cheap goods in an area like this. Nobody can. But now that they're gone, somebody will succeed with a small, overpriced grocery store that pays local teenagers minimum wage and has a produce section the size of my bathroom. And even that store will go downhill over time as the people with money continue to pass away and move out.
I wish I knew the solution to this problem.