Dollar General and their ilk are behemoths compared to the shops that might have served these areas before they rolled in. It's possible they're the only game in town because they engaged in dumping or other dirty/illegal tactics to drive out established businesses.

I'm not an expert on the topic, but I don't think it's a reach to think that they might have engineered this situation.

My point is not to explain how they caused it, its to point out that the commenter didn’t even mention the existence of that possibility