Not sure why you are being downvoted given that this is probably correct? Sounds like the attack was through an admin portal. Given that Trump was one of the few high profile accounts not targeted, it seems like the attackers were not able to access his account through that portal. And his Twitter has been attacked by employees before so Twitter probably locked it down so employees can't modify it.
Maybe not everybody with internal tools can mess with it. Because somebody with internal tools already messed with it before and it didn't look very well for twitter. So if there's anybody with brains there they probably made some measures so it won't happen again.