What is Mark Zuckerberg up to right now? He's doing a lot of of outreach, and even meet and greet tours. It's a bit like he's on the campaign trail, planning on running for political office, but maybe not exactly that. e.g.: https://www.ft.com/content/b0a6481e-d20a-11e6-9341-7393bb2e1... http://www.telegraph.co.uk/technology/2017/01/04/mark-zucker...
I don't think that he'd want to manage a company that just fights off rivals. Becoming a politician and (trying to) make a change sounds more like him. He has the money, people mostly like him and he'd only have to find a CEO for Facebook to get rid of conflicts of interest, as he isn't involved in many other businesses.