Fact is, there are many contributing factors, and not one sole cause for such an accident. Such as: The prevailing Wx, System's Health (Flight Control System and other things that have been mentioned here), Pilot fatigue, disorientation, incapacitated due to workload, mental and physical health, and many many more that I can't think of right now. So, we shall wait to hear what the summary of the investigation has to say. But DO bare in mind that aircrash investigation is not there to find the GUILTY, but rather to find the REASONS for why it happened, how it happened, and how to prevent things such as this to happen again in the future.
Philipp