Another view that humans are attracted to violence as an end in itself. There are a lot of them and they do well at the box office. Humans also fight over property. Hobbes - if any two men desire the same thing, which nevertheless they cannot both enjoy, they become enemies. And in the way to their end, endeavour to destroy or subdue one another.
Hatred is another cause of conflict.
We seek revenge against those who have done us some harm. Many wars have been holy wars - so religion can be a cause of war. Leaders need the backing of other significant elements in society, including the defence force, to conduct a war. They can make a lot of money out of wars. Another cause of war is hegemony - when a powerful state seeks to spread its influence through military means.