DALE AMON OF SAMIZDATA HAS SOME THOUGHTS:
I suggest there was damage to the TPS on one wing, causing a burn through and structural damage leading to failure of the wing structure when aerodynamic forces built. The shuttle has very high wing loading, so any loss of margin would be disastrous. If one wing fails, the shuttle will immediately roll violently into the direction of the failed wing followed by god only knows what sort of tumble. It would break up into major components almost immediately. That is what we saw on the clip.
There would be very little fuel on board. Only some remnants of RCS fuel, a lot of hypergolics for the APU and perhaps a small left over from the reentry burn. Almost all off this is at the extreme rear in the two lumpy bits either side of the vertical stabilizer.
A second scenario is catastrophic failure of the APU’s taking out all the hydraulics just when they are needed the most. With or without structural damage directly caused by such a failure, the shuttle will go into uncontrolled tumble and breakup.
A third scenario is fatigue failure. I don’t feel this is likely, but if so we can kiss our manned space access goodbye.
I give almost zero credence to ideas of terrorism being involved. Ten years ago predictions were for the loss of one more shuttle during the space station construction, just by pure probability (“If it’s not one damn thing, it’s another”). We all prayed we’d continue winning on the dice toss but ultimately knew we’d roll snake eyes.