My personal suspicions?? (1) Either there really was a tile issue -- maybe 3 or 4 damaged in a single area -- that permitted a whole to be burned through, disrupting the aerodynamics at this crucial stage; or (2) Something simply broke or warped, the computers detected this, and corrected for the aerodynamic error badly enough to tumble the vehicle.
Either way, the telemetry should point to the effects - if not the cause.