There has been a tsunami that killed over 10000 people and demolished multiple cities and dozens of chemical plants and factories. If this was a man-made disaster where the fuck was the planning to prevent it? Why are we still talking about the nuclear plant, where at most a couple of dozen people will die in the next hundred years?
Sure, we could have done more to prevent the damage in Fukushima, like build units from a newer generation (fukushima daichi's sister plant survived the same tsunami, but was slightly younger and thus had much less problems), have better oversight, regulation, emergency response etc. However, that is like asking what could have been done better about shark deaths in Nevada ("noone expected it to happen", "zomg, sharks!"), and totally ignoring deaths by drugs abuse, cancer, transportation accidents and cardiovascular causes in the meantime.
The point is, reinforcing Fukushima would have been a waste of money and effort, money and effort that would have been better spent on building better flood barriers to protect places where people actually live.