I think that is the point. He is doing it to increase earnings, he isn't doing it for shareholder benefit, it is for his benefit directly. He could forego some growth in revenue in return for not destroying his users privacy but he, Zuckerberg directly, elects not to.
The stock price would likely tank. Besides being ousted. That’s another reason not to do certain things. Making Zuckerberg into some boogeyman seems over the top.
He owns less than 50% of the company but he controls more than 50% of the voting shares.
Let's say FB starts losing money or spending it on really useless stuff, sure the secondary stock price could tank, but that might not matter to MZ at some point.
Yes it is. However in general a CEO has to do it "for shareholder benefit" as the shareholders could vote the CEO out, this it is useful for a CEO to blame decision on the need to get a return for shareholders. Zuckerberg has the shares set up so that shareholders have no voting rights, they cannot get rid of him. He could forego some profits by introducing some level of customer privacy and he would be safe from being replaced. That he doesn't means that he himself must take all responsibility for pissing on users privacy.