I agree that Twitter could have been run better, and I also agree that there might be some overhiring here and there. However, what is happening in Twitter is extreme. He randomly fired half of their workforce, which made many others leave. And now, if the rumours are true that 75% of the remaining are leaving, we are talking for less than 1000 people remaining in a company that had over 7000 workers. I do not think that 700 or so remaining employees, however hard core they are, can do the job that 7000 did in the past.
Now of course, Twitter will start hiring, and luckily for them, Meta just fired 11K people (although most of them in not-tech), Argo AI closed (so 2000 good workers there), and there are other layoffs in other top tech companies. At the same time, he basically fired every recruiter, and even at the best of times, recruiting takes time (checking your CV, talking with HR, talking with hiring manager and/or 1-2 screening interviews, followed by 5 rounds of technical interviews and 1 behavioural interview, with a committee reading the assessments and deciding to hire or not, often followed by a VP checking the decision with veto power). Essentially, it is very hard to do this in less than a month, and quite often it goes 2-3 months. To make things even worse, there are entire teams who have been fired, so who is gonna do the inteviewing for those roles. With entire teams fired, it means that there are entire parts of the codebase/database/infrastructure that no one doesn't even know what to do with, entire features that people are not aware, let alone know the codebase. If Twitter starts hiring fast, it means that the current engineers need to spend a significant amount of time interviewing, rather than writing code.
In other words, it looks like a total clusterfeck.