Zuckerberg isn't dynamic enough or even enough of a character (think Trump) to rally up enough people to win an election.

He would get a great deal of votes for sure.

But among other things, lack of the wow factor, and well this was one of Hillary's drawbacks. Ditto for Mitt Romney.

The main thing he has going for him is name recognition (a big factor for sure and honestly the only reason anyone would take him seriously as a candidate).

And despite what anyone thinks of Trump he did have a great deal of life experiences with a wide range of people (of all types) in multiple businesses vs. Zuckerberg who essentially went from dropping out of college to Facebook. As such I am not sure of his innate decision making ability given that most of the things he has accomplished have been done with handholding of the people around him.