Walmart starts to sell them, sells tons of them. Tells the red flyer company they want to be the exclusive customer and they expect deadlines met. Walmart had put a lot of the other companies selling red flyers out of business, so the red flyer company is kind of in a quandry and has to comply with Walmart. This went well for a while until Walmart started demanding lower and lower prices - red flyer company can't lay off or they can't meet demand... so the whole dang company gets sold off and goes to China where they sure can meet the price point and demand. In fact, Walmart makes a bundle on the red flyer wagons because they aren't any cheaper now than when the red flyer company made them in America.
The town that red flyers were manufactured in was devastated because a lot of other storefront businesses are affected when a company goes bust.
About 24% of everything Proctor and Gamble sells is sold at Walmart. With this kind of buying power Walmart can dictate the specs to which the product is manufactured.
This is one of the ways they are able to sell cheaper. Clothes are made cheaper by using lower cost materials with lower threadcounts. Walmart also has fantastic technology to manage their supply chain. Within an hour of a purchase the specific shoppers information has left the store and in in their main systems. They use this to track individual shopper buying habits.
They also use this technology to control their suppliers. Many suppliers are not paid for their product until Walmart sells it.