The Columbia was moving along at a rather faster speed...I figure, soon as the spacecraft began to tumble or spin, it came apart very quickly.
Always figured dear ol' Dale never knew what happened...maybe the same for those Seven Stars over Texas.
Up until the moment of disintegration, they probaly were observing the data feeds, watching the autopilot correct that left drag...and when they crossed the line to unstable orientation, they explode a second later...things happen fast at 12,500 mph.
The astronauts were torn to bits...the pictures of the shoe and helmet are proof of that.
The patches falling all the way intact remind me of the paper and post-it debris from WTC destruction...out of that cloud of fire came floating down whole sheets of note and letter paper, photos that had been on desks, as if they'd been tossed out the windows.