TEPCO were morons. WHO builds a nuclear facility near a shoreline ... IN earthquake country??
Their other oversight, was to not have installed tech to remove any build up H2 gas in the rooms, which had been standard improvements to the same basic reactor designs in the US for years, and which would have prevented their severe post-tsunami complications of hydrogen explosions. Which spread the radioactive material around and greatly complicated their clean ups.
AND with the backup generators placed where easily flooded...