The third reason, is dramatic irony. Dramatic irony is when the audience knows more than the character. This provides another source of tension for the audience- they know the character has been taking the WRONG PATH.
There are two that know sometimes amiss. The audience knows. And one of the other characters knows. This is another character who has already learned the lesson, the same lesson that main character ignored. Later we'll learn more about the specifics of this journey. For now, we're exploring the overall shape of our structure.
In the beginning we set up what was at stake if the character succeeds and if they fail. We've now shown the audience what will happen if they succeed. They've hit the glass ceiling the we set up.
Can you put together what happens next? That's the beauty of this structural shape, everything is organically connected. So it guides the mapping out of your story.
Here's some clues for what happens next. A few cliches come in handy...
"Be careful what you wish for."
and "What goes up..."