Engineers have to do their calculations and get their sums right to make sure that those margins are there, and society expects them to do so, which is why it's all the more alarming when things like this happen.
Les ingénieurs doivent  bien effectuer leurs calculs qui assurent que ces marges existent, et la société s'attend à ça. Ainsi, c'est d'autant plus alarmant quand des choses comme ça arrivent.