William levitt was able to create affordable homes in postwar america by

Lowering cost of building by making his own wood and nails and broke down construction process into 27 separate tasks and assigned each task to a group of workers who would go from house to house repeating their specific task at each building site. He would also have truck drop off what ever they needed right where they needed them and make people who clean the house, add flooring/tiles/painters/etc in in turn for each house to make it go faster 

Because he proposed that all the treaties should be made through the league of nations.