The supply chain is functioning normally, but "normal" means ~40% of food consumption in urban areas occurs via restaurants. The supply chain isn't designed for 100% of folks buying groceries at the supermarket and preparing their own food.

And that's sort of the problem. The normal centralised supply chain optimises for normal usage patterns, and adapting to abnormal usage patterns causes widespread issues in the short term.

A decentralised supply chain is (at least in theory) better able to adapt to local distrubances.