Also, there is actually no hard evidence that the cabin even lost pressure.
But there is also no reason to assume, that there should be much cabin left after a 22g acceleration. Its way beyond what the various components in the cabin had been designed for. It is even very likely, that some overhead panels had been ripped out of their frames at that acceleration.
And the collapsible seats had likely also failed beyond 15g. Likely leaving only the commander and pilot capable of doing anything useful.
Even if the crew very likely was alive before impacting the ocean, it could easily have been different. There was a lot of work involved to turn the Shuttle cabin into an escape capsule. Much more then just sticking some KSP parachutes to it and hope that all will work fine until free fall.
The same also applies to re-entry capsules BTW. You have to design everything in them for the task and make sure it really keeps its promises.