Why did the war start anyway?

I was particularly interesting in why WWII started, and only a few decades after the first World War. It seemed weird to me that after so much destruction, the countries of Europe, and followed by other countries in the world, would want even more? I discovered in my research that France, Britain and the Soviet Union actually provoked war primarily in their attempts to maintain peace with Hitler, and therefore with Germany.

Britain and France wanted peace, and Stalin sensed Germany was out of control and tried to unite all the anti-fascist countries. He also wanted peace, and was convinced that Hitler would not start a war against the rest of Europe if they were strongly united. However, while Britain and France were anti-fascist, they were not fans of the USSR's communist regime either. They didn't want to unite with Stalin so they desperately tried to keep the peace with Germany so they wouldn't need an anti-fascist alliance. This is what pushed Britain and France to easily agree to the Munich Agreement, in which Hitler promised peace so as long as he got to take over Sudetenland. This move lost Britain the support of the Czech Army, but they were convinced it has prevented war and did not want to go to war with Germany over the seemingly small matter of Sudetenland. However, Hitler, being the bad guy he was, went against his word and invaded the rest of Czechoslovakia, breaking the Munich Agreement.

Before Hitler broke the agreement however, Stalin was becoming suspicious of Britain's deals with Germany. The Munich Conference was something Britain would normally support, unless, Stalin thought, they were trying to force Germany onto the Eastern front instead of the Western front. By now, Stalin was convinced war with Germany was inevitably. However, this didn't mean Germany had to be fighting Russia. He figured Britain was probably thinking the same thing, and was trying to push Hitler to declare was on the USSR. Stalin tried to buy time to build up his army by signing a peace treaty with Germany. The countries had always argued over Poland, and the Nazi-Soviet pact was signed on August 28, 1939, agreeing to share Polish territory. This certainly took the world by surprise. Fascists and communists had always been enemies. However, barely 4 days later Germany invaded Poland (after trying to convince the world that Poland had invaded them first, which of course was not the case) This was the last straw. War was declared on Germany on September 3rd, 1939.

With the Munich conference and the Nazi-Soviet pact, it is clear that Russia, Britain and France were desperately trying to maintain peace with Germany. However, with Hitler so out of control, the treaties were broken, leaving the Western and Eastern fronts with absolutely nothing gained from these treaties and plenty lost. This was what eventually started another World War.