See photo at # 40 for a bit more damage - and many improvements have been made since then in structural analysis.
Looking at the crack protuding more than one frame forward, this might have already been far beyond the required damage tolerance capability and that crack my have grown up to the door if the fuselage would have been fully pressurized...
Crack stoppers are required to stop a two bay crack (one frame/one stringer lost, two skin panels cracked). Initial damage beyond this might indeed cause full desintegration.