Walmart quickly becomes a local monopoly, because they dominate over the local competitors who cannot leverage the same economies of scale to lower distributor prices nor afford to bleed money in one area in order to take over the local market.

Honestly it seems you either refuse to read what I wrote, or you are invested in a free market ideology. The link you posted is nothing more than a hard-libertarian free market fanatic opinion blog, heavy on snark and lacking in value.

Read about the damage Walmart does to communities and why even their mere presence in the market completely distorts it:

https://money.com/walmart-stores-closing-small-towns/

https://www.citylab.com/life/2012/09/radiating-death-how-wal...

https://popularresistance.org/new-report-wal-mart-destroys-l...

https://m.dailykos.com/stories/2013/03/28/1197622/-The-Walma...

This goes for all megamart chains, Amazon and the like, but Walmart is among the very worst.