Why did this happen ! 

http://www.facebook.com/photo.php?v=517630311635209

Interesting comment on Youtube.

Quote
Yes, a 747 can fly on 2 engines (maybe even 1) but it can't climb, and particularly not with a full fuel load and cargo, and climb fast to avoid becoming a target. If heavy cargo broke loose (like a vehicle) it would slide down the fuselage to the rear bulk head pulling the tail down and increasing the angle of attack. Airspeed would drop AND airflow disruption over the wings resulting in an aerodynamic stall. The plane would wobble, roll and dive. Gain airspeed and regain lift. But too late.

:O

Perhaps data from the black boxes might show the cause.  I don't know if the boxes record audio but if it did you would hear if anything broke loose in the cargo bay.  If the black box recorded a sudden pitch up without pilot input, that could also indicate the CG shifted. 

I don't think there was a complete failure of the flight control surfaces because you can see the pilot trying to correct until impact.

just imagine what the conversation inside the cockpit would be like! :O

They were professional, fought till the last second, and thought of their loved ones at the end.

^ +1

http://www.nycaviation.com/2013/05/the-death-defying-job-of-a-military-charter-loadmaster/