In total, there were four main causes of WWII, Appeasement, Hitler's Actions, the failure of the League of Nations, and the abandonment from Hitler of the Treaty of Versailles. Besides the league of nations factor, the rest of the cause were all because of Hitler. This means that the majority of of WWII was caused by Hitler.
France and Great Britain gave Hitler and Germany appeasement in order to avoid war.
The treaty of versailles put harsh restriction on the size and the ability of Germany's army.
The Treaty of Versailles also forced them to pay back all war debt which made Hitler very upset and he began to start war.
Some countries in the league of nations were reluctant to send troops to aid other countries
The League of Nations failed
They only met 4 times per year so during emergencies they had to have a meeting which could not take place fast enough
The league's main power was to just not trade with aggressive countries so that they run out of supplies, but other countries still did which aided them and not hurt them.
The fourth and final cause of WWII was Hitler's action. He abandoned the Treaty of Versailles and began to take over Europe at a extremely fast pace which then forced other countries into action to stop him