Seems to me twitter should hire some humans to sit there and manually approve every tweet by all VIP accounts before they go live. How hard could that be? If that’s all they do you’re adding maybe a 30 second delay to every VIP tweet and you’re pretty much guaranteeing that this doesn’t happen again. Unless of course the hackers somehow inserted the tweet directly to the database and bypassing any such measures.
That will not help, as the imposter could post a sane tweet impersonating the VIP. The person checking would not be able to identify if it's the VIP or the imposter.
The point is to screen outrageously out of character or dangerous tweets, for instance Hillary Clinton giving away bitcoin, or a politician declaring war on another country. Something timid or benign slipping through is not that big of a deal.