Elbaf is not Usopp's Arc. It's SH's Arc
Elbaf has Nine Mountains, each SH will fulfill their Dreams above those Mountains
Zoro's Name will reach Heavens (Top of Mountain)
Usopp will become Brave Warrior of The Sea (Prove himself to Giants)
Sanji needs to find All Blue that connects all Oceans (It's basically a Superior Version of Reverse Mountain)
Chopper needs to find All Healing Cure (Hiriluk told him about Story of a Guy who got Healed in a Mountain)
Franky needs to Build Ultimate Ship (Who will Help him build it? Giants obviously)
... etc
Elbaf is Final Destination for Nine Straw Hats
And They are the ones who are gonna Fix the World, not Luffy
However, their Actions do not last, because "Nothing Happened" it's just a Lie, a Fake Story, a Dream
That's where Luffy's Role comes in, He is the Man who will make his Crew's Achievements a Permanant Reality
That's what One Piece does, basically the entire Story/Adventure didn't happen, it's Fake, except the Final Chapter
Only Final Chapter is Canon, The Rest is Non-Canon
However, One Piece cannot be Activated unless Final Villain is Defeated, hence why Luffy is the one who's gonna carry everyone's Dreams
Because Reality depends on whether He Wins or Loses (Warrior of Liberation)