Why didn't they follow the mandated procedure? Was it because they hadn't studied it or briefed it and were therefore unfamiliar with the procedure or the correct track to fly while descending into the valley and easily distracted by the offer of a straight-in landing? Which they had every right and responsibility to refuse by the way, if they felt they couldn't make the adjustment in the time remaining? Allowing the aircraft to complete that left turn was an unconscionable error for anyone sufficiently familiar with the procedure and aware of the nearby terrain.