Walmart has a clever / corrosive effect on brands.
Walmart can marshal insane amounts of demand.
If a brand is about to invest in brand-building marketing spend, Walmart forces them to invest in lowering the price instead.
This benefits consumers and Walmart, but it harms the supplier.
The supplier becomes increasingly dependent on Walmart, and Walmart has more leverage over them.
Premium brands might be hollowed out by consumers seeing them as cheap, transactional.
It's a monkey trap: short-term benefit to the brand at long term cost.