The auto throttle (not auto pilot) apparently got a false altitude reading from the left hand Radio Altimeter, actual altitude was 1950ft (as right hand RA indicated) but it reported an altitude of -8ft. The pilots noticed this, but did not think this was a problem (from CVR). The auto throttle however reduced the power to idle to prepare for the flare, as though it was just some feet above the runway.
The throttles remained at idle untill the stick shaker engaged and stall alarm went off, by then they were too slow and low to recover.
The further investigation will focus on faulty radar altimeter / auto throttle interaction and pilot reactions.
Personally, I find it strange the pilots did not notice the reducing speed untill they stalled.