MIT caps the foreign students in a class at about 15%, so you were competing for one out of a bit over 150 slots. You very possibly made the "Can you do the work?" cut; overall, before applications shot up from 13,000 to 18,000, about 1/3 made that cut, but MIT has room for only a bit over 1,000.

It's nothing personal, and the people involved in admissions do not like turning down qualified applicants, but they don't have any choice.