Interesting challenge to select a single cause. Perhaps easier to consider the primary hazard, the ground.
Continuing towards the ground, i.e; below minimums, without being able to see it should, for any reasonable person, introduce an escalation of risk that is unacceptable. In addition, proximity to the ground reduces the time available to diagnose and apply the correct recovery action.
Add inexperience, both pilots manipulating but not co-ordinating the aircrafts primary controls, increased stress levels, tiredness, etc this may well be classified by the coroner as an accident but to aviation, and maritime, proessionals this event was predictable albeit the magnitude was not.
Rolling or excessively banking this aircraft would take it beyond certified limits and into the realms of upset recovery (UR) for the crew. These are not practised in the real, commercial, world and not accurately modelled in the simulated world, but nevertheless should be recoverable with sufficient altitude. Generally, 'below minimums' is insufficient altitude to recover from such an upset.
Last edited by darkbarly; 6th Jul 2014 at 15:13.
Reason: typo