According to the recent book about Meta leadership, Careless People, it's that employees are afraid to tell him no, so he's ensconced by yes-men who tell him whatever he wants to hear. He probably has no grasp of market and product development realities.
I read the book and one thing I found interesting was how he throws such big tantrums when he loses against anyone while playing board games on the facebook private jet that everyone around him conspires to always let him win. Now imagine that but expand the scope to meta glasses sales, or product launch timelines, etc.
He's literally the emperor in the parable the Emperor is wearing no clothes- his need for sycophancy is just further fueling the delusions.
> how he throws such big tantrums when he loses against anyone while playing board games on the facebook private jet that everyone around him conspires to always let him win
It's hard to believe that that is a real person and not a fictional person being written against some trope.
I never noticed that the Emperor was a vain man who couldn't admit his lack of wisdom (because only wise people could "see" the beautiful cloth, and he pretended to be able to see it), and that he was surrounded by yes-men (of course he was surrounded by similarly vain men who had to pretend to be wise to keep their positions, but I didn't notice how this turned them to yes-men).
Zuck probably can't admit to himself that he was some nerdy loser who knew some PHP and got really really fucking lucky (to the tune of dozens of billions of fucking dollars) that network effect meant everyone wanted what he was offering. I'm guessing he thinks those billions must be proof that he's smart... So smart that he's unbeatable at any board game.