It certainly doesn't hurt when the government profiles and grooms intelligent people out of Stanford SRI the dark side, Harvard, hands them an unlimited credit card and says, "Make this thing that can do x,y,z." and then helps them network with like-minded creators and removes any obstacles in their path. One has to at least admit that was a contributing factor to their success as the vast majority of people do not get these perks.
Intelligence probably IS positively correlated with success, but the formula is complex and involves many other factors, so I have to believe it's relatively weak correlation. Anecdotally I know about as many smart failures as smart successes.
There are many things we can and should say about Zuckerberg, but I don't think that unintelligent is one them.