Re: Monotheism
You're confusing symptoms with causes.
Most of human misery at the hands of other humans has been about one human or group of humans seeking power over another group, or taking their wealth. Preferably both.
If God, Jehovah, Allah, Zeus, or any other gods figured into this, it was primarily as a convenient excuse. Blaming monotheism for warfare is like blaming flies for garbage.
Not much has changed. If you strip away most of the rhetoric from modern politics, it's still all about the power and wealth.