Great company, but manager is brutal with 0 leadership skills - Anonymous employee Synopsys Employee Review

My manager makes my life at work miserable including his/her entire team. Very short fused. Holds grudges. Sharp tongue. Always angry. Has no mentorship skills. Yells at team in front of stakeholders. Snaps at stakeholders. Very forgetful, therefore, always contradicting what they say. Makes directions on what they want very confusing because they change their mind constantly. There have been so many complaints to my managers manager already. He/she got a very poor ratings last year and still no change. Most everyone on his/her team ready to leave. Why has upper management and HR not stepped in to do something?