That and those reactors were pretty much the only things left standing after the earthquake/tsunami. They were engineered for large earthquakes but 8.9 right off the coast was beyond even reasonable predictions. In fact they did okay through the earthquake (well, maybe offline#4's coolant pool problem was more earthquake than tsunami) and it was the /generators/ that had issue after the tsunami. And a 23 foot wall of water's pretty hard to plan against.

Re the generators someone commenting on one of the npr articles figured that water covered and got into the fuel reserves, then sank to get between the fuel and the intake.