A jumbo jet airframe just isn't designed for violent maneuvers. Once it went out of control, it's actually quite plausible that stuff started falling off.
Speaking more generally, everything has tolerance limits. Your TV set, a baseball bat, the human body, jumbo jets ... they all are designed, whether by man or God or nature, to only be able to withstand a certain amount of stress before physically breaking apart. That stress can be from G-forces, temperature, pressure, age, any number of things.
Think of it this way: Imagine you found a way to supercharge your car's engine so that you could suddenly drive at 800 mph. No funky attachments or anything, just a few simple alterations to what's already under the hood, and whammo, you've got SuperCar. Now imagine actually attempting to get it up to 800 mph. Go ahead and presume you're alone in the middle of the desert and have plenty of room to go in a straight line without having to worry about any of the normal hassles of driving like other traffic; it's just you, the car, and an empty landscape.
Now think about how your car acts at normal speeds. Think about how it operates at 25 mph; pretty darn smooth. Now think about the speed limit, around 70 mph. Perfectly acceptable, but the ride's somewhat bumpier, wind resistance affects your driving a bit more, etc. Now imagine really gunning it ... up to 100 or 110. Now your car's really being buffeted by the wind, it's somewhat harder to control, you hear creaks and jiggling and clacking that you don't normally hear, you can see the antenna really getting bent back somewhat, etc. Now roll down your window for a moment. Oops. Pretty nasty. Tolerable, but unpleasant.
As you can see, as the speed increases, the stresses on your car's frame (and engine) increase as well. Now imagine the jump from 100mph up to 800mph. Assuming that your own body could even handle the G-forces without you passing out, imagine what would happen to your car as it kept being pushed closer and closer to that magic 800mph limit ... eventually it would just start breaking apart. The wind stress alone would just start ripping pieces off ... the antenna, the rear view mirrors at first, then more vital pieces ... then pieces of the engine would start failing, because while you may have found a way to make you car's engine go 800mph, it doesn't change the fact that the engine's parts were never designed to be able to handle that sort of speed, that many RPMs, that high of an oil pressure, etc.
It's the same concept with the jumbo jet, except in many ways the jet is actually far more fragile than your car. There's a reason they have to have a cursory inspection every single time they land, a serious detailed inspection after every X number of flight hours, and a total stripdown and rebuild every couple of years or so. (Here's a very nice thread explaining the various levels of checks commercial airliners must go through, in both technical detail and in a simplified way that compares each sort of check to what its equivalent would be in the auto world (scroll down to "Avioniker's" post for that one).