> People also vastly underestimate how hard it is to produce commodities.

Neither Amazon nor Walmart produce those commodities, they distribute them. Sure, there would be some initial issues, but both the remaining distributors as well as the producers would have strong incentives to quickly resolve those issues.

Obviously there would be temporary shortages in some areas heavily dependent on Wal Mart, but elsewhere where Wal Mart is one of 20 similar stores, the surrounding businesses would be able to handle increased business. That one Wal Mart suddenly closed to prevent union forming and the town survived. Brick and mortar in general would have growing pains but also adapt.

Of course they did—the same way they bought things at the local mom & pop stores before Walmart came in, undercut them, and drove them all out of business.

Companies like Amazon and Walmart massively distort the market, and do so quite deliberately. It's hopelessly naïve to think that if they vanished tomorrow, everyone would be able to just shrug and switch their purchasing to a drop-in replacement.

That's only possible in, as someone else described it, the "spherical cow in a vacuum" type of hypothetical free market. We live in the real world, where an arbitrary number of fully equivalent businesses can't actually continue to compete perfectly for everyone's money.