Simple: he's crushed because he had a dream of going there - he wasn't framing it as "I'm better than everyone else." As I mentioned, it is his dream running into reality. So saying "not being in the 0.1% as a teenager is tacky" is not the right framing because he wasn't thinking about it that way - he just had a dream and now realizes how difficult (and unlikely) it is.
Regarding your kid: There are 4million US high school graduates each year. MIT admits about 2000.
Sorry for being abrasive, but why is your child crushed that he isn't the very best? Why is it sad that he isn't better than everyone else?
Being upset about not being in the 0.1% as a teenager is tacky. 99.9% of us aren't.