Of course they "are successful because consumers prefer them", that's kinda definition of being successful. This is saying nothing. What would be a little more revealing is to give a real explanation of why consumers prefer them. And, as it happens, a whole lot of this explanation would consist of what basically is dumping, very dubious anti-competitive practices and other things that kinda-sorta are considered violating antitrust laws. And sometimes it is so blatant, that I can only admire the virtue of lawyers managing to keep this thing afloat. And antitrust laws exist for a reason as well, because game theory offers plenty of ways to make people choose what is worse for everyone in the long run.
So saying there's nothing intrinsically good about "mom-n-pop" stores compared to what Amazon is is a very dubious thing to say. To re-iterate, sure, consumers chose Amazon for a reason, but things are not black-and-white and deciding if something is good or bad is far more nuanced than just that.