Well in the end game evil people do not succeed. You can have cooperation because of mutual self interest but as soon as you lose power that cooperation ends. I had people help me when I was at the lowest of my life, knowing the they would never probably been repaid. Zero self interest ,only loyalty, friendship and justice. With that help I smashed evil while it never expected me to survive.
Plus... I do not know if it's for me only but often, when people do really bad to me, they get heavily punished by the universe shortly after. Evil self destroy because it is hate