Earlier quoted context omitted.
The quote also doesn't indicate the SpaceX team is being "brought in to overhaul FAA systems", that seems like a big mistake if that tweet is all they are basing it on. The tweet says the FAA is tasked with overhauling their ATC system, and people from SpaceX are visiting to share ideas, and it seems to include an open invitation to others to do the same. Political pettiness, and speculation about whether Musk got so…
Maybe Musk should have done that review before firing all of those FAA employees last month. Maybe those jobs were important.
It's been reported that 400 new hires on probationary status were let go. None of them were involved in safety related operations. The FAA has around 45,000 total employees, so it's a rather tiny percentage, in any case.