There was a case in 2017 of a Twitter employee who deleted Donald Trump’s account for 11 minutes.
In 2020 hackers who gained access to Twitter admin tools that were - at the time - apparently accessible to thousands of employees were able to use that access to compromise multiple verified (blue check) Twitter accounts including Jeff Bezos, Barack Obama and Bill Gates. They used it to promote a lame Bitcoin scam.
In the aftermath of that things were supposedly tightened up a little but don’t doubt a Twitter employee could do some damage.