It was 1945. Hitler and Mussolini were wiped off the face of Earth. USA had no new Hitler to fear
Actually USA had a new Hitler to fear. His name was Stalin. However 1945 was no 1938. USA was superior in strength due to nukes.
Hollywood still cannot make a movie on Superman comic books. Those who read Superman were not low in strength. Since 1929, adults were either too poor to feed their children or busy in World War 2.
It was in 1945, when adults could fully be available for kids.It was in 1946, when kids would born in large amount than ever before.
Demand of the audience has also changed. After seeing reality after their service in World War 2. No wonder Hollywood did not make many kid-friendly movies like “Wizard of Oz” or “Robin Hood” but realistic noir. In such atmosphere Superhero movies would be too kiddish for audience.
However 1949 changed something. Stalin got nuclear weopen and Communist won the Civil War in China.
What would happen to Superhero in next decade ?