Intact historical buildings and artifacts are rare, because something like this is the expected outcome. People are careless and incompetent, except by accident

Intact historical buildings and artifacts are rare, because something like this is the expected outcome. People are careless and incompetent, except by accident. Restoring a major historical building is always a one-off project. You follow the best practices, and the chance of a catastrophic outcome may be 10%, 1%, or 0.1%. You can't tell those scenarios apart in advance, because they all look very similar. Success is overwhelmingly likely. If a catastrophe occurs, the reason is often obvious in retrospect, and you will take that into account in the next project. But it clearly wasn't obvious in advance.