Sorry to see this disappointing outcome.
Over the coming months, across the country, many stellar candidates who are fully qualified with outstanding packages will receive this news from all 5 SAs. There are always more excellent candidates than there are seats available. This is exactly why there are so many discussions on college re-applicants and Plans B-whatever.
Right move to ask for any insight on improvement.
This is an opportunity for your DS to deal with adult-sized disappointment and subsequent course changes and decision. He will learn to coach himself back onto the path. He will grow and learn from this.
Here on SAF, this process and the subsequent years are often described as a roller coaster ride. Sometimes, unexpectedly, it jolts to a halt and you have to get off. That doesn’t mean you can’t try for the next one, if this is what is truly desired.
News like this does tend to put recipients through the classic stages of grief - shock, anger, bargaining, sadness, acceptance.
Oh - do suggest to your son and take the advice to yourself to not torture yourself with comparing “stats,” noting those who receive appointments with apparently lesser “stats.” NO ONE here can see the entire candidate package, much less in comparison with others, except Admissions.