Europe was still recovering from the war, Russia, East Europe, and China were Communist, everywhere else was a remote backwater that no one cared about. With no competitors, we were fabulously successful.
I would also add that the demographic profile was great. There were huge numbers of healthy adult workers, hordes of little kids, and very few retirees to support. If there are 10 or 12 workers for each retiree, the workers have a lot of money available to spend on their families.
Muscle cars, everyone working and making it good on 40 hours