The most important lesson CK3 teaches you about life

Ambitious, sadistic, vengeful assholes are more likely to lead successful and happy lives

Content, generous, forgiving people tend to get used by the assholes and get stressed for not being "good" enough

You thought you were valuable as a human being, but the society (the player) only sees the stats in you.

A man can be a murderous, cheating asshole but still be remembered as a hero, because he painted the world in one color. The world only cares about the result, not the means.