trying to understand what led a competent crew to end up in that situation
I recall a quote from the Boeing chief test pilot on the 787 project when briefing simulator instructors. He said: " We designed the 787 assuming it will be flown by incompetent pilots - hence all the protections in place."
While a pilot may have passed all required simulator competency tests required by a particular State Regulator, it does not necessarily follow he is automatically competent when flying in command in the real aeroplane. Often ethnic culture is not always compatible with flight safety.