It's not that simple.
Facebook has two classes of shares.
While Zuckerberg only kept 28% of the shares, he kept 57% of the voting rights. So it's still entirely his decisions.
Their entire premise is "We're smarter than the rest of the world and you poor people can't be trusted with the big important decisions of us billionaires." This is social media on the internet after all—the most important advancement in humanity's collective history.