Wow, what a risk management fail. Yes the sub screwed up, but this was also enabled by totally inadequate safety systems and processes.
To my mind this reinforces the notion that it's probably possible to build these things safely, but only if we treat them like the highly flammable hazards that they are.
Would a sub have been able to work like this if they were doing something analogous at a gas station, or in an airplane hangar? If these are going to continue to get built, it seems that it can't be 'business as usual' for the trades....talking about strict no smoking, strict management and validation of heat sources like this generator, strict control on other highly flammable materials, plus continuous monitoring for anomalous heat and special capabilities for rapid response and containment...
... there are many many many precedents for this way of working in other industries. These things are just wicked flammable while they're being built, and they need to be treated like the hazards that they are ... it's very doable, just has to get done (and the insurers now how make all this happen too)....