dumbasses need this to be a very simple answer.
Many many things happened.
The US won WWII and enjoyed a competitive advantage in many industries for the next 25+ years
Technology and automation exploded and continues to since
Treaties and Trade agreements expanded labor all over the globe
a middle class has emerged all over the world....billions of people joined the middle class
The US has seen shifts in political parties that drives shifts in trade and tax policy
I could go on but those are usually agreed upon things that have happened. The argument is how much credit does any single item on the list receive.
The last 1 I posted appears to be the only 1 some here accept as being a real and meaningful event.
Which is absurd. Does it belong on the list? Of course but nobody here has a shred of a clue as to how much weight to place on it.