When the foundation to almost every company’s long-term success is the people it has hired, eviscerating those ranks of people indiscriminately is a really great way to have loads of institutional knowledge flee and the job become much, much harder for anyone who remains.
At this point, my only immediately rational conclusion is that Elon is acting out some sort of a revenge fantasy, trying to create as much harm to Twitter as possible without any care that the company might actually collapse. Or maybe even to that end, explicitly, just with plausible deniability.
These tweets makes some great arguments that give legs to my supposition - anyone with any minimal amount of business sense would know of these arguments, and yet Elon is ignoring them wholesale to the detriment of Twitter. What remains is the determination of whether it is ignorance or intentional malice.