Because a lot of people died in the battle I think
their new lives new technologies such as the radio, silent movies and Henry Ford's automobile industry were invented. And First, it gave Americans more leisure time. By the 1920s, there were many more labor saving devices, particularly ones that reduced the difficulty of housework. These gave Americans more time to do things other than simply working. Second, technology gave Americans more things to do with that newly-found spare time.
