Amazon has done well because they work from different premises than most businesses. In particular, they're in the middle of a multi-decade effort to squeeze waste of various sorts out of the process of buying things.

They're now the best mail-order retailer, and they've beaten out local merchants for some classes of goods. But there's a long way they can go in terms of beating local merchants for most of the rest of what people buy. My guess is that Bezos isn't slowing down until Walmart is hurting.