As I figured...probably over weight...
Bagram 747 Crash Update | Opinion - Conservative
Each vehicle was 33 metric tons - 72,000 lbs. 90,000 over the 280,000 for the aircraft.
Over gross + load shift due to busted straps, locks, bailing wire, whatever they were using, = uncontrollable aircraft.
No doubt a high performance teep departure out of Bagram to avoid ground fire might have contributed to a vehicle jumping a chock, strap breaking, etc...