While we don’t have official numbers, we do have this

https://www.vice.com/en/article/n7z5px/twitter-employees-on-visas-cant-just-quit

Early in the Twitter takeover, Twitter employees were offered a severance package to quit. H1-B workers can’t just leave because they need their job to stay in the country. We can thus speculate that most of the workers that did leave are US citizens which leaves Twitter with the H1-B workers

No one wants to work for him. He’s just holding visa workers hostage