The whole eye of the world is the first time that the dragons power is established. Doing it the way they did didn’t demonstrate any power. Sure he beat that baddie but that’s not much given he wasn’t established. Wiping out the trollocs afterwards is what adds to it. Then finding the horn. Not sure why they took the trollocs and the horn away from him and gave to others.If you are talking about the ending, Rafe said it was to give the girls something to do.