Today is a sad day for aviation, and specially for cargo brothers. All that for a crappy pay check.
The so called, "Tactical departure" and here I am just assuming, must be climb as high as possible, as fast as possible.
If it was load shifting, which it is possible, but the plane had at least one Load Master and US soldiers as loaders, who, and here I am assuming again, checked everything loaded to be in order. That doesn't exclude the possibility, during climb, one or more pallets to snap off and induce a roller coaster effect.
If it was a microburst, it must have been a darn huge one to crash a B 747. I am assuming again, a microburst would have been seen from the ground too, being a very dusty and sandy place. After all we are talking Afghanistan here, which is not the greenest place on the planet.
So, until, some official reports will be out, everything else is just speculation. Personal I incline toward load shifting, due to stress on the load during a steeper turn and climb.