Possibly.
I think you said it was the main factor, right?
One could just as easily say, "To pass off any person's rejection from a top school or slight deficiency in profile to just not being intelligent enough is, I feel, short-sighted." I'm not saying that intelligence is unimportant, because we all know it is. I'm just saying that I think it often gets overemphasized and there's so many other important factors in being successful at anything. Some students go out 3 - 4 nights a week. Other students study or relax on Friday and Saturday night. Some students skim through material the night before a test. Other students push themselves hard the few days before and really try to understand the material. Some study 30 hours a week, while other study 60. If you don't think that these sort of differences are common, then I think you haven't hung out with a wage enough range of students.
Do you really think TMers are that much more intelligent than college students as a whole? Maybe we are, but it seems to me that most TMers are successful because they're driven and have foresight (so they find out what classes they need to take to get ahead, work on getting solid LORs, etc) and I imagine most TMers work pretty hard (putting in the hours, being focused when studying, etc) and making sacrifices (not partying too much, not drinking too often, etc).