Their accounts weren't hacked. It looks like Twitter was and whoever got in was able to get full admin access to the platform. Really not good.
That may be overstating what has happened.
If you had full admin access to Twitter (if a single solitary admin access even exists, which I doubt), would you post a bitcoin scam for a relatively small amount of money, or would you as silently as possible reside in the system, biding your time?
The bitcoin thing might even be a ruse, like a lot of ransomware is. My money is still on some third party being compromised that had saved auth tokens.
Still,as you say, really not good.