During WW II the US went through a massive increase in airport construction and flight training, especially in states like Arizona and Florida.
Airports that were transferred to municipal control or simply sold to the county for the token $1.
So the infrastructure was simply there for people to use.
The state of Florida has 80+(!) public airports and an additional 70-80 private strips airports and air parks where people live with an airplane in the garage.
Flying is so much more "normal" in the US the it is in Europe, virtually everybody that you meet has a relative that either holds a license or even owns an airplane.