Death of the middle class seems a bit drastic. Kind of clickbaity. More like walmart fails to keep middle class demographic.

I feel like Amazon is a big part of this. Amazon isn't always the absolute cheapest, but it is super convenient and easy. If you don't have to pinch every penny you might just do most shopping on Amazon and save the hassle of going to the store.

Target as well has always been the middle class version of walmart imo. Better kept stores and slightly higher prices(at least in my area).