Perfect example of the swiss cheese model, as someone pointed out already!
Which makes me think about the role of the lasf of that slice of cheese which is usually located at the end of the line: the pilots.
We are the ones who have a chance to stop the chain of events that has filtered through several other cheese slices.
The more the talent we have, the better the education we have had, the better the training we have had, the better the selection process in airlines is, the more experienced we are... the fewer holes that cheese slice has.
quality, good training, experience and good selection will result in good airmanship and hence more safety.
Recommendations in this direction should be made in any "swiss cheese" accident.