Economic, political and social.
Instability was from the Treaty of Versailles left many countries bitter for they did not get fully compensated for the war. Germany, especially, experienced economic and political issues bc they had to be a republic and pay billions in reparations. Russia was faced with a revolution and struggled with famine and inflation. Europe was faced with even more instability after the stock market crash of 1930.
It occurred chiefly due to the economic interventionism of the Japanese government and partly due to the aid and assistance of the U.S. aid to Asia. After World War II, the U.S. established a significant presence in Japan to slow the expansion of Soviet influence in the Pacific.