How the hell did they miss so many cues and just basically sitting there and watching the aircraft crash?
The pilots didn't miss the cues. The cues were obvious all the way down the flight path but were ignored. The answer to your question is in the blind culture of the operator and similar operators in that region, where protection against loss of face is considered a higher priority over airmanship and flight safety common sense. It is not as if this event was just an isolated case.