Speculation induced Fatigue and complacency?
The possible causal factors are enormous. Was it the aircraft or the crew? History has taught us that it could be either.
From the very little evidence available it is unfair to cast aspersions about who may be responsible but it is going to be discussed anyway so is best to be non judgmental.
From where the impact occurred, if a go around was initiated at a low altitude my guess would be a fairly rapid loss of performance. If the aircraft is innocent then it is probably environmental or crew. The weather does not look that bad.
The most likely way to cause a large performance loss that the pilot flying and the aircraft can not recover from is to retract the flaps more than the procedures call for.
This has caused accidents in the past and has been the focus of much training world wide including in EK.
It still happens today during takeoff and go around through fatigue and or complacency. Aircraft performance on a good day is enough to cope with these slip ups, hot or high altitude or mild wind shear combined with retracting too much flap to early would cause an aircraft to hit the ground in the same region as EK521. The crew most likely would not even know they did it.
In a complacent state crew operate on the most likely automatic response expected without conscious thought.
After the landing configuration is attained the PM is programmed by routine that the next time the flags need to be moved is during the complete retraction after landing. In a fatigued or complacent state the call for flaps during a go around could initiate a greater flap retraction than desired.