The free market is not what is creating sprawl. Sprawl is created by policy effectively outlawing anything but cars. Also, cars are convenient when everything is designed for them and pretty much them alone.
https://en.wikipedia.org/wiki/Streetcar_suburb
Cars enable more suburban development, but their throughput on highways sucks compared to mass transit, which also minimizes their spread in some cases.
There is a minimal critical mass to enabling them to be effective and we're not at it because laws.