The company was already bleeding money. He might fail to save it, but can he really kill a company that was already dying?
He may have done far worse things as well but that depends on your opinion of his product/feature changes. But the additional debt he has saddled them with and the revenue he deprived Twitter of aren't really arguable, and his attempts to cut costs by short term slash and burns don't make anywhere near the dent needed to offset them.
I don't like Musk but is this a mercy killing?