Columbia was much higher when the breakup occured. I believe over 200,000 ft. The astronauts would have been unconscious immediately upon breakup. A great book to read about Columbia is Comm Check
The book "Comm Check... The Final Flight of Shuttle Columbia" by Michael Cabbage & William Harwood went into great detail about how NASA's crippling bureaucracy didn't fix the problem that caused the second disaster.
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https://www.amazon.com/Comm-Check-Flight-Shuttle-Columbia/dp/1439101760