Many previous ICO hacks (wait for initial coin offering -> change the bitcoin address to your own) have paid millions. Musk's or Buffet's tweets have moved markets multiple times. This sort of access could have been leveraged to gain at least x100 more than what they achieved.
Moving the market doesn't do anything if you don't have the stocks. This might have been a temporary hack where the hacker was not sure how much time he has. It could be simple as someone gaining access to an unlocked home PC of a remote Twitter employee.
