There is a false belief that FDR’s unprecedented peacetime economic interventions got us out of the Great Depression and thereby saved capitalism from itself. Why do you believe so many people believe this incorrect statement?
Different people can believe things for different reasons. In this answer, let us look at some of the most common reasons why people might believe this.
First, it is because the statement is not completely false. The New Deal was unprecedented in its scope. It did not get us out of the Depression, but it certainly did help to ameliorate the effects of that Depression. There were plenty of other countries that became much more radicalized during the 1930s and it is at least plausible to argue that American communists or socialists would have gotten much more traction had President Roosevelt not pushed for these programs. Thus, there is at least some truth to the statement, and that helps cause people to believe it.
Second, we are much more likely to accept stories about our history that identify heroes than those that talk about broad forces in history. It is much more uplifting to be told that President Roosevelt saved us from the Depression than it is to be told that only the onset of World War II was able to save us. By saying that Roosevelt saved us, we get to have a story with a hero.
Third, this story helps us feel better about ourselves. When we hear this story, we can tell ourselves that Americans always find a way out of their problems. Even when we are faced with something as catastrophic as the Depression, we can overcome our problems. If we give credit to the war, we become much less capable. Instead of saving ourselves, we were saved by something completely outside of our control. This does not make us feel good.
Finally, much of our history has been written by liberal historians. Liberals believe that government intervention in the economy is a good thing. Therefore, they are more likely to believe that FDR’s actions were efficacious. They also want to see Roosevelt as a hero because he pushed for policies that they approve of. This helps cause them to give FDR more credit than he deserves.
For all of these reasons, we tend to believe that FDR’s efforts put an end to the Depression and saved capitalism.