Cazatou
You said:
What exactly was the fault that caused the crash?
Easy question to answer: There may or may not have been one.......and the possibility that there may have been one is sufficient to cast doubt over the cause, convenient as it is to blame the pilots.
Alternatively, try answering this question:
What exactly was the fault that caused the US Army Chinook to roll in the opposite direction to that intended, resulting in the pilots of that aircraft having to roll through 180 degrees before regaining level flight 850 ft below the starting altitude? I'll even give you a clue: although the aircraft was landed intact, no mechanical fault was ever found (apart from the pilots' report that full rudder was needed during the manoeuvre).