Hi all...
So Dragon quit the Marines because of the horrors he saw in GV, Ohara just made him go up against the world government and their island "erasures" (Ohara can be GV 2.0 here since they both disappeared anyway).
Also Dragon most likely saved baby Shanks, later on adult Shanks saved kid Luffy like an indirect returnal of favor.
It all makes sense that Dragon happened to be at GV: "A child is a parent's weakness".
So Dragon quit the Marines because of the horrors he saw in GV, Ohara just made him go up against the world government and their island "erasures" (Ohara can be GV 2.0 here since they both disappeared anyway).
Also Dragon most likely saved baby Shanks, later on adult Shanks saved kid Luffy like an indirect returnal of favor.
It all makes sense that Dragon happened to be at GV: "A child is a parent's weakness".