The dig is three fold. (if the story is true, about which I have my doubts.)

One: Elon instead of cultivating an organisation where the right people are rewarded and the wrong people are selected out tries to personally weed out the wrong ones. That is fundamentally foolish even if he is firing people who should be fired.

Two: His subordinates don't respect his decision and instead of letting go the people he wanted to fire, they "hide" them in the organisation elsewhere.

Three: He is too distracted / stupid / incompetent to then notice that his decision has been undermined.