What is King of Spain actually about to you, and why does something so silly on paper hit the way it does?

To me, “King of Spain” is about using fantasy to escape feeling small, lonely, or powerless. Becoming a king is deliberately absurd, but he sings it with such sincerity that the joke starts to feel like a genuine wish for another life. It hits because the silliness never cancels the sadness—it gives him a way to admit it.