There’s more to the exchange (that I can’t find right now - I read it on Twitter…) where Halli acknowledges that Musk has the right to lay him off for whatever reason. He said he was merely trying to find out if that had happened or not.
Musk publicly apologized to him, so I presume there was some threat of legal recourse against Twitter.
One thing Musk ran into early on as Chief Twit was that most countries have laws protecting employees, particularly regarding layoffs. He tried to lay off EU employees the same way he did US employees, and broke a myriad of laws in the process.
It’s possible that he ran afoul of Icelandic employment law. Also, ghosting an employee might not be legal, even in the US.
Apparently, Thorleifsson was the CEO of a company acquired by Twitter in 2021. He said he decided to sell the company, that he founded in 2014, because his health was failing.
As part of the deal, Thorleifsson had a contract with Twitter that would pay him $100 million if he was terminated early. Perhaps if Musk had texted HR before popping off on Twitter…