As I said on the other forum, telephoto pictures are always deceptive. What looks like the rocket exhaust could just be the rocket or a portion of the structure on fire. It uses a hybrid solid/liquid fuel design, and thus might continue low-grade burning after the explosion. Think of Challenger, and the solid rockets tumbling with fire coming out the nozzles.
Don't have any data available yet, so we don't know at what altitude the event occurred...or even what the target altitude was for the day's test. A minor explosion could have compromised the vehicle's structure sufficiently to cause it to break into major components WITHOUT spreading the wreckage very far. The aft fuselage, with the motor, might then start a tumble that would position the nozzle forward.
We know it wasn't a major explosion...not only did one of the occupants live, but intact parachutes were seen. It may have just been a "pop" which, combined with aerodynamic forces, broke the vehicle up. Or even caused a sudden "up elevator" action and the Gs pulled the thing apart.
Ron Wanttaja