Before this industrial innovation, workers were used to manufacturing goods in a made-to-order basis, this means that a worker would be considered good in one thing and they would make that and help to build the product to the end.
Once the assembly line and mass production came, products were made more quickly and with fewer costs. This lowered the prices of goods and also lowered the wages of workers because they did not need to be specialized in something, they were needed just for some parts of the production system.