In an effort to try to bring this thread back to a technical level, suppose the rudder control went "stupid" and started to travel back and forth, from stop to stop, on it's own. Wouldn't the severe yaw motion that would result cause the engine pylons to fail? My thoughts are that, like most other air disasters, this one resulted from a combination of problems that all met at one single point in time.
1. The tail assembly had some structural damage from either original manufacturing or a subsequent incident.
2. There was a problem in the rudder controls that the mechanics did not find or fix that morning.
3. The PIC used some heavy feet in trying to fly out of wake turbulence.
So a plane with a defective tail structure takes off with a problem with rudder controls. The problem doesn't present itself as a solid problem until the pilot hits the controls hard in an effort to fly out of turbulence. The control problem now presents itself by slapping the rudder from side to side; sort of the opposite of a rudder hard over. This causes (or starts to cause) the engines to seperate. It also causes the original structural defect to fail entirely, seperating the vertical stablizer from the aircraft.
This is all conjecture on my part, but I don't see any other clear cause. I'd love comments by some of the more non-emotional members on this theory.