Looks to be pilot error, sink rate was too high, tried to correct a the last minute, smashed the tail on the seawall and the rest of the events unfolded. Kinda sad. 777 is a magnificent machine, to have it's perfect record of no fatalities ruined by what looks to be a failure to manage the approach properly.
This ^
The 777 is a magnificent plane, her only flaw are the humans that fly her.....
While of course it is too early to tell if it was pilot error, the video shows too low, too slow.......the NTSB comments that they were 'significantly lower than target airspeed, the early indications of a stick shaker stall warning, the late attempt to go around....all point at something gone amiss in the cockpit.
Cockpit Resource Management is of paramount importance..... occasionally Pilots fixate on seemingly minor events, and forget to 'Mind the Store'....... resulting in tragedy.
I suspect that something caught the attention of the crew.....and they forgot the most basic of all rules...... 'fly the plane'