I bet the reason Trump didn't get hacked was because he is special-cased in the Twitter system to avoid insider vandalism which protected his account from this insider attack.
I believe you are right, a rogue Twitter employee had previously[1] deleted Trump's account. So there must have been some special protection to prevent it from happening again.
Agreed, it could be as simple as someone at Twitter calling someone in the White House every time someone logs into the account. (The White House has a ton of staff, I met some of their IT people at a conference back in the day.)
I bet the reason Trump didn't get hacked was because he is special-cased in the Twitter system to avoid insider vandalism which protected his account from this insider attack.