Because no man is an island, but heckuva many are peninsulae. Success is much more than merely intelligence, tenacity and hard work. Success is the ability to cooperate, use the connections, teamwork, friends, social ties, organizations and hierarchies. To howl with the wolves.
There is the nasty thing of communication range which is the root cause of this issue, why people with unusually high IQ are more likely lonely than not.. Nobody gets successful alone and on one’s own merit only..
According to several intelligence researchists, all meaningful human interaction can occur only on certain bracket of IQ – the communication range. According to Leta Hollingworth, it is +/- two standard deviations (30 points), according to D.K. Simonton, it is +/- one standard deviation (15 points). Once the difference between two human beings’ intelligence becomes too great, all communication becomes impossible.