Also, I find it particularly interesting how Mark is so focused on pushing everything into the public "news feed" style sphere, and seems to have a kind of wishful thinking involving messaging in particular transitioning from a private activity you do with your friends to this public bombastic twitter-esque landscape of public figures "sending messages" to their followers and removing the barriers between those communications and "real" communications between your actual friends. He seems to intensely believe that this is really the only way to create a giant business - essentially destroying and corrupting personal private connections to fill your experience with "more engaging" public content to keep you addicted to the platform.
Well, especially for chat, that didn't pan out. And now we are entering a period where private stories, private communication, and meaningful communication matters more - Instagram growth falling to single digits and rapidly losing ground to other platforms among younger users (a harbinger of things to come) - Mark's dogmatic commitment to the alter of public newsfeed paradigms has caused almost all his platforms to evolve towards a dying entity one by one - all except for, notably, WhatsApp.
One gets the sense that Mark has one trick, and that trick is no longer effective at meaningfully growing and positioning FB for the future, especially compared to its historical growth rates (maybe those were unsustainable anyway).