It's not if nothing works, it's what works when nothing works, i.e. the safe thing must always work. period. (i'm not trying to be pedantic or an ass)

Safe in this kind of context means no property damage or no casualties or no injuries. Not no financial damage. Sometimes repairable property damage is accepted if that is active or passive safety component.

That is the point of failing safe. It would me much worse if some of the trains kept running...