I never really thought of it as such, but good and evil exist and we have an innate understanding of them. And since good and evil exist there will be a meting of justice to make things right.
Since we have no rhyme or reason to bad people getting their just desserts in this life and none to good people having over-the-top bad things happen to them, there can be no expectation that things are different when we die.
It is silly to think there can be any kind of expectation of what things are like after we die basing our assumptions on this life.
It depends on your definitions of those things. I could argue that God has done more evil things than any human. There are people who do good and who do bad, all at various times. There is no indication-- none-- that there is cosmic justice that rewards good and punishes evil. So, it's not rational to believe in "good" and "evil" in the way you mention.
It is silly to think there can be any kind of expectation of what things are like after we die basing our assumptions on this life.
It's no more silly to make expectations based on stories in a book. There are many religions and they have varying-- wildly-- beliefs about the afterlife. None has any more logic than another.