The geopolitical reality of World War Two is that it was a collection of smaller, weaker powers challenging the biggest empires on Earth. These empires got to where they were not through democracy and freedom, but military expansion and conquest. The Axis powers were each trying to correct an imbalance in the power held by these empires vis-a-vis their own nations and they ultimately failed because they didn't have the resources and manpower to overcome what the large empires could throw at them in a long war of attrition. The common theme of Germany, Italy and Japan is not that they were big, scary, all-powerful militarists but rather that they each unified late into the 19th century while Britain, France, America and Russia were busy conquering and exploiting whole continents. Each developed a strong culture of military discipline not because they liked war and loved militarism, but because they were weaker and more vulnerable than the resourse-and-manpower rich world empires surrounding them. This weakness is why Axis coordination was so bad during the war and why the Axis powers could never effectively support each other.

Some people would say then the mistake was challenging those world empires in the first place—and that Germany, Italy and Japan should've just accepted foreign domination (as they have ever since 1945). That may be so, but it doesn't change the fact that the Allied victory had nothing to do with morality and everything to do with 19th century imperialism and conquest, the same thing the Axis powers were morally condemned with after the war. This is why the League of Nations was derided by the Nazis as “This noble society for the moral defense of former acts of violence”—that's all the United Nations was intended to be, also.