It is possible a single engineer was negligent or even malicious, but I would rather believe the whole organization was at the very least encouraging a culture

It is possible a single engineer was negligent or even malicious, but I would rather believe the whole organization was at the very least encouraging a culture of "do whatever to be ready at the end of the quarter and I don't want any detail" (orally of course) You can't be reckless in a place where everyone is paying really close attention to safety and regulations. On the other hand if you are in environment where everyone is pretty lenient, it is much easier to slip between the checks. But, from a journalistic point of view, even if the story is not fabricated, it is a better story to have a villain, than trying to convey to the readership how complex organizations (mis)behave.