Best to worst culture - Regional Manager QUEST Alliance Employee Review

I’ve worked at quest for around 4.5 years. When I joined it, I’ve got a chance to experience the best culture that’s very employee well-being centric. Gradually things started changing with entry of one person who has kicked out entire CB team and is always only a mission to fire existing people and hire people aligned to her views. Regionalism at its peaks. Mind games at its peaks. Almost taken jobs of 10 people. Management is well aware of all of this but still stays shut. I’ve never understood why. What are the directors HR team And CEO doing.