So sorry for your son disappointment. It can’t be easy for him. My mother used to say everything happens for a reason and it will become clear why the road you are traveling took a little detour. Over the years I’ve found this to be true.
He said it knocked him out of his socks at first. That's been six weeks ago. Meanwhile, while still in and "being processed," he saw things that most people never see. That has tempered his disappointment. He's changed, for the better. Grew up a few years in a few weeks.