Here's why:
* Theme is the central idea or message that the author wants to convey through the story. It's the underlying meaning, the "big picture" that emerges from the characters, plot, and setting.
* Plot is the sequence of events in a story.
* Setting is the time and place where the story takes place.
* Characters are the people (or sometimes animals) in the story.
While plot, setting, and characters are all important elements of a story, the theme is the core message that unifies them. It's what the author wants the reader to take away from the experience.