In the short-term, Zuckerberg maybe the CEO, but if he keeps prioritizing ads over product (which he has done with FB prod/privacy), then the long-term maybe dicey.
Just as content is king, so product will always be king. The ads will follow whoever has the best product, and hence user attention.
Ad money is what lets him crush or acquire competitors. The thing that isn't discussed is how commodotized social media software is. Sharing photos and comments and likes is the core of these businesses and it's extremely easy to replicate over and over from a tech perspective. The hard part is acquiring users, scaling and monetizing and FB has won that game. That's how they can take anyone else's product or idea and best them at it so quickly.
Just as content is king, so product will always be king. The ads will follow whoever has the best product, and hence user attention.