There are always more than one side in any conflict and most of the time they are not as clear as in WW II, but I argue that wars are always started because of material gain besides other factors.

Look at the British empire, they exploited their colonies to the max taking all the resourses for themselves. They didnt invade india just to have power over it. They did so for the wealth of their own country. So did every other colonizer. The US wages wars over oil or to to keep the world as capitalist as possible. Russa is waging war in Ukraine not because Putin wants to holiday in Kiev. Israel wages war over the question who is allowed to prosper on that land.

Not every act of aggression is about money, but I do believe that one of the root causes for every war is material gain.