I think profit and power, or the lack thereof, can be the root of a lot of these awful human traits. It can just be straight up greed driven by a few looking to gain power and/or money that push an agenda of [insert tried and true bogeymen here like xenophobia, religion, racism, etc.] to create motives and instabity to trigger the wars. It could be genuine problems like economic issues or severe agricultural deficiency, via real misfortune or more likely due to greed, corruption, and mismanagement by the country’s leadership. Even religion can be the rationalization, a tit-for-tat, but nonetheless the end result is to take what the enemy has. It doesn’t have to be formalized markets or capitalism.