@matiapa, your son’s credentials are very fine indeed.
Nobody KNOWS why your son wasn’t admitted except to say that it’s a very competitive landscape. #1 in the national physics olympiad is very impressive. The reasons you’ve been given are PURE SPECULATION.
These decisions should not take anything way from your son or be any reflection on his self-worth.
Does your son still need help finding a place to go to college? There are still good colleges accepting applications.