The correct answer is Appeasement
The appeasement policy was a measure taken by European economic powers (England and France). It consisted of not stopping the advance and popularity of Nazifascisms, with the intention that Nazi Germany and fascist Italy would bar or even fight communism in the USSR. Since these countries, Germany and Italy were opposed to the communist idea.
This is the biggest and best explanation given as a reason why the economic powers have done nothing to stop Nazism and fascism.