After the Civil War period in 1920, business operators were able to boost their profits by reducing costs for consumers. They could do this by lowering manufacturing costs.
If you lower the manufacturing cost of your product, then you can sell your product for less money. The cheaper the product is, the more likely people are to buy it. During this era there was not that much competition, this gave companies using production lines an advantage over other companies that couldn't make their products as fast.