I kinda felt like this was an article that had a missing Character, like covering the 2016 election but not mentioning Bernie or Comey.
The reality is that Walmart's Chinese-sourced non-food goods (including clothing, auto parts, and general household supplies) were priced 50+% cheaper than many non-food (and higher profit) items one could get from a grocery store, once you're at Walmart then, well you're at Walmart. This, combined with the insane Dollar General growth mentioned likely is why many of the local stores died. I always kinda felt that this kind of marketing positions sometimes actually harm the market, kinda like how Amazon's $50 android tablets trashed the non-iPad market by taking all wind out of their sails.
Also, for those not familiar, dollar General is not a dollar store as its name implies. They sell cheaper, lower quality items at a markup vs department stores but their secret weapon is incredible organization efficiency with cookie cutter free standing stores that are made simply using cinderblock construction and templated layouts. Their turn around after starting construction to store opening is less than two months at a very low cost in strategically placed places that lack close grocery/department stores. If you made a heat map of all the grocers and department stores in a rural area in the northeast with red for 'near grocery store' and green for 'not near', the dollar general onslaught would almost exactly be an inverse map, identifying low income areas. This is even true in suburban areas where driving is required to get to a grocery store, with dollar general's popping up in the projects.