It's actually an incredibly unprofessional comment. He's just labelled a bunch of ex-employees as being unimportant, not having made it and going to a graveyard. People change employment for lots of reasons; incompatibility, working conditions, family commitments, career prospects and these comments are really bordering on defamatory. I'd be hesitant to work for any employer who trash talked former employees, it's just unprofessional.
Yeah, Tesla actually hired those very high skilled people, they worked a while for them (putting long hours, I'Ve worked in the valley) and now moved on for greener pastures; that happens all the time down there.
So, is Tesla's HR and management team so bad that they hire all those "bad fit" people... If that's the case, maybe HR, management, or the way work is done, needs to change... If people leave, it's often for VERY GOOD REASONS, and it should be a big warning sign that something's not right, not a notice to lash out at those who flee.
I doubt that even a minute portion of them were actually let go for performance reasons.
So, yes, his comment was beyond crass; a douche move.
If I was getting an offer from him, I'd wonder how soon he'd think that about me?
Would he have this king of thinking while I'm still there, pushing me out in some passive-aggressive way because he was too lame to tell me to my face, and just waiting to be fed up and leave because that made him feel like the "good guy"...
(A bit like many people do in a relationship... They're never to blame if it goes sour... Never)
Considering how many comments from Musk we've had on Apple and the rumors of poaching, I think Apple is probably biting pretty deep in his talent pool, even delaying his plans, and it pisses him off.
There's only so many talented senior expert engineer in such a field and not every one of them wants to have to have to prove that they can "cut it" when in fact they know what they're worth already (and the competitors do to). Musk is not recruiting in a vacuum; his words are very bad for future recruitment.