Why we are always unforgiving?

Can someone tell me why we are asking for the head of Met. Police commisssioner, when the woman commandor who was leading the opration, which went wrong and resulted in unfortunate death of an innocent person, got promotion. I know the top man should accept responsibility but surely not not at any price when we rewrad the negligence of one and punish the one who was relying on of one his senior officers, whom is not mention in any report for failing to do her job in the first place.