[panopticon]

Their AmazonBasics line has been very successful and incredibly anti-competitive too.

Before you go and compare it to brick and mortar in-house brands like Walmart has, consider that Walmart has a higher investment in things they end up stocking in store (they pay for things up-front and shelf space is comparatively scarce). Amazon doesn't have the concept of "shelf space", and Amazon doesn't paid for the product up-front in many cases.

Walmart is notoriously pushy on suppliers, but once product is on the shelf both Walmart and the supplier's interests are heavily aligned. Amazon would rather peddle you their Basics line instead.

[actuator]

Walmart's interest are only aligned till they can cut a better deal with some other brand or they come up with their own product.

[panopticon]

I didn't ascribe any virtue to Walmart's position, but it helps to illustrate how Amazon is able to be much more effective at corning the market.