I will try to be Rational
The Mag 9 quake and massive plate movement in 2011 was well beyond the magniutude any ,repeat any Seismologist considered at all probable in Japan.
It is obvious from many of the comments that knowledge of Seismology is almost non existant.
The Japanese have extensive experience of earthquakes andTsunamis and had built many barriers to protect their coastal areas .
They were to protect to the extent that the risks evaluated , and from what I know were considered elsewhere to be very prepared for such an event
It is foolish and ignorant to propose that a country should prepare for adisasters that are extremely unlikely to occur.
It would go broke and the people would starve.
However, I expect you will continue to rant about something you are totally ignorant.