As my sibling comment describes, this wasn't unknown. TEPCO (the company operating Fukushima) themselves commissioned a report into the suitability of their eme

As my sibling comment describes, this wasn't unknown. TEPCO (the company operating Fukushima) themselves commissioned a report into the suitability of their emergency systems, came to the conclusion that a generator and switchgear room in the basement of a building next to the sea was a bad idea, and then did nothing about it for several years. They were also told this repeatedly by other agencies.