Earlier quoted context omitted.
It's because people want to feel like they have a purpose. It's the same reason you see Hollywood actors being outspoken political activists. Because if they stay out of politics, they're "only" insignificant entertainers. It's the same reason you see comedians and TV shows getting political. Saturday Night Live (SNL) is just a show for laughs. But if it takes a political stance, suddenly the writers/producers/actors…
I might be inclined to believe it if it weren't only so many words. Where are the actions to back up the argument? Internet.org? India would like to kick internet.org in the nutsack. Giving money to charity? Where are the results from that investment? Without any evidence, Mark Zuckerberg is just another king of spin. Aren't there enough cockroaches in the world already? Not saying Mark is one, but I'd like to see so…
While this manifesto was a little over-the-top, and probably amplifies globalism as a cure-all, he does appear sincere in his desire to do good. Time will tell.