You can't use an NDA as a way to bar someone from discussing a crime. Also, even without a crime, the NDA only imposes civil penalties for a breach, it can't literally prevent you from speaking, they can just come after you for the agreed upon penalty.

Your mom: How the f--- did you forget a tie? Your dad: Don't have a cow, man!

Can't say this with certainty. But Tesla and SpaceX could sell the vision of being the first successful electric car company and commercial space venture, respectively, to employees. People who cared about those ideas would more likely tolerate a shitty CEO because they believed in the mission of the company. Not sure Twitter has that same greater purpose to overcome his fuckwittery. Especially since his fuckwittery often runs counter to what Twitter was before he took over.