Sad news. Hard to discuss without knowing the facts like aircraft history, pilot training history and background(used to low vis ops or just trained but not so often used it), and especially from the work threads here in the ME part - how many hours have they previously flown(week/month/year) and which quality of rest they had before this flight.
We do not know anything about that(well, some may) and for this reason we will have to wait for the actual results of the investigation from the RUSSIANS(don't thrust the GCAA as well with that).
RIP guys.