Hindsight is 20/20.
If they designed the generator systems for a 7 meter tsunami, eventually there will be one 7.5 meters.
Every solution has another problem associated with it. This is the reality of engineering. If we succumb to the fear of failure, nothing would ever be built.
This is similar to the fear of flying. A person thinks the flight they are schedule to take will crash. So they decide to change the flight. Then the flight they were first supposed to take landed safely and they have yet to take off. They again get scared and decide to drive instead only to be killed by a truck but the other plane landed safely also.
There are no definite answers to anything. Each person thinks they have the answer to this disaster. But you have the luxury of knowing what already has happened. The engineers don't have that luxury because what happens is in the future. Engineers must deal with these types of questions on a constant basis. But statistics and the freak 7 meter tsunami will inevitably come along because the chance is not zero. That's the way life is.
Here's the bottom line, this is not Armageddon. We, collectively, need to accept the safety hazard of nuclear power. Far more have been killed by being hit by spinning wind power turbines.
This is news, and people might die, but compared to the thousands of bodies washing up on the shore, it's nothing.
We need nuke power, ASAP.