According to preliminary information from the CVR, the decision about approach was taken by the crew themselves. Direct cause of getting too low - wrong altimetry, wrong wx data or busting the minima not yet announced. It was also said that in final moments crew was aware of iminent disaster and that it was too late to recover.
A/c flipped to its back before crashing, hence the reason everyone on board perished - similar accident of Tu204 near Moscow recently claimed no fatalities.