1) Harvard has to make its decision on the basis of limited information.
2) Even if Harvard had perfect information, there are probably more 'ideal' candidates in the world than Harvard could hope to admit. Most are still going to be excluded.
3) Just because Jack Ma has become successful doesn't mean he would have been a good fit for Harvard. Success in entrepreneurship is not the ultimate educational goal for all (or even most) people, and does not necessary reflect all the qualities that a school like Harvard wants in its students (except, cynically, the ability to make big donations later in life...).
So where does this leave us? Don't beat yourself up if you don't get into Harvard. Most successful people didn't. But, at the same time, actually going to Harvard (and schools like it) remains an incredible opportunity for those who are admitted and have suitably aligned educational goals.