"Bigotry and fear were used to promote and justify the suburban life, but they were only tools, not the founding principles. I think the real driver was simply the energy gradient created by the discovery and development of fossil fuel."

There is also a less insidious reason. Don't forget GIs following WWII: They returned "home" - but they didn't actually go home to the farm. After they'd seen Paree, thousands of people settled in big cities and the newly developing suburbs. It was the "modern" thing to do at the time.