There are various complex and interrelated catalysts of World War II. When Germany's National Socialist German Workers' Party took over the country, they replaced the old regime and political structure, and yet the Nazi Party essentially continued the old regime's vision of European dominance.
Prior to World War II, even though the German Empire tried to maintain a balance of power with its allies, it was also caught in an arms race with Great Britain and France. This showed that Germany was trying to gain more power through military might and was concerned that the other powerful nations in the continent would have an advantage over them.
The transition to peace after World War I was still in effect when World War II erupted. This is due to the fact that World War I was something of a prelude to World War II. For instance, Germany had suffered defeat during WWI, and its economy took a big hit. There were massive unemployment rates, hunger, and social and political discord. This environment led to the rise of Adolf Hitler and the National Socialist German Workers' Party, who used an extreme form of nationalism to "cleanse" Germany of those who they believed had caused the economic situation in the country.
War, in effect, brought the economy back to life because it created a manufacturing boom. The dynamic between the war and the economy was symbiotic. The economy fed the war effort, and the war fed the economy by creating new industries. In fact, some of Germany's largest automobile manufacturers, such as BMW, were a direct effect of the war economy. The same can be said for Great Britain and the United States. The United States had just survived the Great Depression when they entered World War II, which created massive industries in the US. It also established the US's world dominance.