In every war or conflict or strife, there is an aggressor and a defender, the aggressor is the one who wants more for themselves, whether being a country, community, or individuals, and the defender is the one who wants to defend what they have, also being a country, community, or individuals, and there is always that party which is not from either of the sides but is the party that benefits the most in every conflict, those who stir wars, conflicts, and strife.
Throughout history. there were wars, for whatever reason, from reading much about all wars I can assure you that the vast majority of such wars are for greed and to control more resources, some of the wars fought were by people who needed food and were not helped out by others who they attacked, in very rare cases. There is no such thing as a religious war, all such wars were pushed for by political reasons and behind it were always greed and desire to control more, they use the religious purpose because it's the most effective way to move the masses.
Imagine in Medieval Europe, if the kings and princes told their people we need to go to another continent just to expand our properties, they won't have enough troops ready to follow them and of those forced to do so they will not have the spirit to fight, when religion was included: we need to go to defend the holy land, then people were mobilized, despite that the holy land was living in peace and the Crusaders only went to kill, loot, and destroy, like currently NATO and Israel in the holy land.
In all such conflicts, there are a group of people, very few of them, who get to 'advise' the decision-makers to start wars and conflicts, to stir the public to riot after convincing the rulers that they don't need to share the wealth with the public, those are the only beneficiaries of wars throughout history, they don't fight, they lend money and weapons to the fighters and they reap the profits, they come in the shape of bankers, weapons makers, and rebuilders, those who will rebuild what the cannon fodders destroyed.
These war profiteers are pure evil.
Image source: New Syria FB page.