If what I’ve read about MZ is correct, he was “placed” in that position and the CIA was the real developer of FB.
So if that is correct, he definitely knows he’s a fraud. Can’t be good for one’s self-esteem.
Even if he really did start FB, it’s clear he did a lot of dirty dealing with co-developers and stole a lot. It’s also likely that his business model includes massive profits from selling data to the CIA. One can speculate whether that is the major source of his riches. In any case, he has to know he’s a total fraud.
I’d understood his Univ buddy created it and Suckberg stole it after being asked to help with it for some reason.