Ugh. Nose high power on stall right after takeoff... Could be a few causes, none of which really mattered to the crew. I do hope they find out the problem so maybe it could prevent it from happening to another flight.
Still...
Trim incorrectly set for takeoff
Flight control or hydraulic malfunction
Uncommanded elevator movement
Incorrect CG before takeoff
Load shift after takeoff
Elevator failed to move for whatever reason (not sure if these things have control locks?)
Physical damage suffered on the ground or shortly after takeoff leading to flight control malfunction
Pilot error
Pilot seat shifts aft at rotation and pilot doesn't release controls (I talked to someone who saw a Cessna 172 do this on takeoff...)
Many of these can probably be ruled out (or confirmed) by wreckage analysis. Not a fun job though, made more difficult by the location.