This incident happened is due to the cargo door is not well designed. The door is opened outwardly and not like others opened inwardly. And the pin lock is not properly locked with this kinda design. I get shocked when I saw such a design. How could a aircraft producer taking risk of the people's life? Very first incident just happened with 60 over passengers in 1972. The plane's cargo door just blew off at certain altitude. And there is a big hole which suck the things out. Lucky that the captain is able to control the aircraft and landed safely, there is no people injured or died.
After that incident, they were asked to modify the door. BUT, next incident just happened like that in 1974. Door blew off, and the captain fail to control the plane and get crash into forest. No one survive through that incident. Later on in 1979, same aircraft happened again. It lost the first engine and makes the plane lost control due to some reason. 271 on board passengers plus 2 on the ground died.
Can you imagine in 70s to 80s, such aircraft company choose to make money and forsake the life of people? Luckily we are sitting on Boeing or Airbus. Not MacDonnel Douglas aircraft.