I thought the same thing for a little bit. For personal reasons I have studied the BOAC accident (Flt 911) quite extensively. I have a copy of the official CAA report at home. The sideways 'gust' that hit the airplane had an acceleration of over 7.5 Gs which was plenty of 'oompf' to remove the vertical stabilizer and all four engines.
I don't know what the ultimate loadfactor is on the vertical fin/engines of an A300 (or any passenger plane for that matter), my guess would be around 4.5 Gs or so. To produce a sideways gust of turbulence of such strength would take quite a bit of doing. What brought down BOAC911 was a severe gust of 'mountain wave'. Now a 747 is nowhere near the size of Mt Fuji, though I must admit, if you've ever seen a dust cloud reveal the 'wake' of one after takeoff I can assure you it's bloody impressive!!
If the tail and engine pylon structure were somehow weakened due to previous structural damage, bad maintenance or some other 'unknown' factor, I would imagine that in theory it's possible for a nasty wake to take it off, but it seems highly unlikely that a jet would take off with its tail structure weakened plus! both engine pylons????, unless that poor airbus was in similar condition to the old VW Rabbit I had when I graduated from college?? I know aircraft maintenance these days is somewhat of an issue, but that would almost be laughable.
What was the airspeed at impact?? What was the other damage to the empennage as a direct result of the fin breaking off?? Could this damage have propagated to the rear pressure bulkhead?? What was the cabin pressurization at the moment of the accident. Where do the flight control hydraulics / control cables come together in the A300?? Tail??? If these were damaged by the failure, and total control of the aircraft was lost, vibrations during overspeed could have taken off the engines???? Pure speculation I admit, but something to think about??
Hey Smolt!! I wasn't aware of the existance of a book on the subject of BOAC 911. Have you been to the crash site? Is there some kind of a memorial? I'd be particularly interested in finding out if there exists a complete passenger + crew list for the flight?? If you know anything more I'd appreciate it enormously if you could drop me an email (firstname.lastname@example.org)