And so what? You have to believe in these things for them to have any effect, so we are talking psychology, not physics.
The model of good and evil entities controlling existence is a popular one. Zoroastrianism is perhaps the best examplar. The Good God takes credit for everything positive, and the Bad God accepts the blame for the negative. Obviously this doesn’t work in a zero-sum situation, such as one cupcake that can only be eaten by one person, or a war that one side wins and the other loses, but it’s a pretty good model, and you can always provide explanations to the exceptions. You eat the cupcake, you get fat, you die young. The defeat set the stage for a stronger and more resolute society. There’s always something the spin doctors can come up with.
And that extends to everything, surely? Viktor Frankl managed to find something positive in his transit through the death camps. Good and Evil are just states of mind, rather than anything connected with reality.
Trying to limit philosophical discussion to the concrete, physical world is a pointless exercise. We’re never going to have enough resources to settle every question to universal satisfaction.
Positing a world where theists and atheists are opposed on every possible point is ridiculous. Some beliefs are shared, some not. It depends on how much Koolade has been consumed, and how adequate one’s education has been. I’ll cheerfully believe in some aspects of Christianity and reject others. Does that make me a Christian? If so, what variety? Gospel of Lukewarm, maybe.