Why War? What seems to be the causes behind the war as depicted in the Iliad?

Back then it seems that the only reason for war were the petty necessities of a king. They justify their reasons for war by saying it's for their land, or for honor, but in reality, wars were waged due to the weakness of kings. In the Iliad, the main reason for the war between the Greeks and the Trojans, was because one women left to Troy. Her departure ignited the flames of battle, causing the kings greed to make the decisions rather than settling things peacefully.