The co-pilot was on one of his first trips on the type.
The third crewmember was a so-called buddy pilot who comes along in case something happens to the captain. He can then assist the inexperienced co-pilot in landing the airplane.
From this we can assume that a fair amount of training was being conducted on the flightdeck making it ever more strange that a slowly decaying airspeed went unnoticed.
Let's recap the events.
The aircraft is fully configured at 3NM in approx. 1000ft with Flaps 30 on speed and on glideslope.
The vertical speed seems a bit high though as with an airspeed of 150 knots approx 800 ft/min rate of descent would result in a 3 degrees glide path.
The approach looked fairly normal until 600ft in regards to glide path and speed.
Then something odd happens as the speed starts to decay.
For some unknown reason(s) proper speed management was not maintained, or maybe they assumed the autothrottle was still engaged when it was not.
The mistake was only noticed very late down the approach and they were caught without options on a low energy/low altitude scenario.
They tried to initiate a GA (survivors state a sudden increase in engine power shortly before impact).
There is not enough altitude to recover and with the ground approaching fast the pilot instinctively pulls the aircraft into a low speed stall.
Witnesses on the ground describe nose high attitude, followed by a dive to the ground.
The aircraft hit the ground tail first in a high rate of descent with low forward speed. This is obvious from the photos of the crash scene.
In my opinion this accident was caused due to the pilots inability to maintain the proper approach speed.
Maybe they were distracted by something as it seems they never checked in with the tower after hand over from the approach controller.
Waiting for the FDR and CVR information to be released.