Switching to the new provider was a bad idea, because it is not that hard to find competent civil engineers who could tell you that rather than being a mysterio

Switching to the new provider was a bad idea, because it is not that hard to find competent civil engineers who could tell you that rather than being a mysterious unquantifiable risk, putting the new chemical in the lead pipes would cause a problem. "Every decision that went badly was a good decision if it seemed good at the time," only holds water when it's not easy to figure out in advance what's going to happen. After all, to a sufficiently ignorant person, 50% of all decisions seem better than average.