She was never meant to run the place, but she's friends with a board member, which a lot of times is synonymous with "you got the title," so she started rebuilding the company in her own image. Whole teams vanished overnight. Employees walked around whispering, hoping to stay off her radar. And the general manager became a figurehead while she made every actual real-world decision.
This is what happens when HR stops being support staff and starts acting like ownership. But give someone a title, a friend on the board, and zero accountability, and you can count on them to rewrite the social contract of the workplace.