Before the days of Levittowns, Sears (yes, that Sears) sold pre-designed, mass produced houses that could be built from kits. These were sold from about 1900 until the 1940's. Just how did Sears of all businesses decide to create the model of the "mass produced home", and why did they eventually quit the business?
Sears did not create the model... Aladdin Homes did in 1906 (Sears started in 1908).
The brothers who started Aladdin got the idea from "knocked down boats" that were being sold at the turn of the century. See here for more info: http://www.sears-homes.com/2015/01/the-last-man-standing.html
Sears was already selling building materials, and it made sense for them to sell the plans and all the materials to build a house. Homeowners made good customers, buying carpets and furniture and dishes and garages, etc.
Sears exited the business in 1942. During WWII there were restrictions on residential building and also restrictions on lumber and other materials. There was nothing in the annual report that said why the Modern Homes department was closed, but WWII seems like a logical assumption.