My point is not about deliberate criminal behavior (such as sabotage) but simply making mistakes. Designing and building an airliner is an incredibly complex undertaking, and most mistakes are "obvious" only in hindsight.
I recall one where the vent for dumping fuel turned out to be upstream of the cabin air intake. Eventually, an airliner needed to dump fuel, it was sucked up by the cabin air intake and the vapors blown through the cabin, and of course it blew up.
It sounds like "how could someone have made such a mistake!". The cabin engineers were a separate group from the engine people, that's how.
Another crash happened because a maintenance worker taped over the pitot tubes to protect them when the airplane was cleaned. He forgot to remove them afterwards. The tape wasn't very visible, and the inspection missed the tape. The airplane took off and crashed. The maintenance worker was prosecuted for his mistake. I felt sorry for the poor bastard - not only did he have to live with the guilt, but was jailed as well.
P.S. if someone in the aviation industry comes to work high or drunk, and makes a mistake while under the influence, I have no issue with prosecuting them.