1945 saw the first horrific use of nuclear weapons on the populace.
The world started to see via radio and tv broadcasting events worldwide.
Communism was feared by Western Society.
The opposed super powers were in fear of each other's military advances. The introduction of the ultra horific Hydrogen Bomb became a reality.
There has always been the ups and downs of a man made economy and employment vs. unemployment
New diseases,getting control of existing diseases added fear.
Crime increased, morals decreased as a result of WWII.
I'm sure there are other valid reasons.
They were uncertain as to what would happen. They didn't know who would be in charge of the government or how that rule would affect them. There was no guarantee of Jobs or income, or knowledge of who was alive, dead, or had a house to come home to after the war.