There's no excuse for obvious mistakes. This wasn't something tricky. There are hundreds of years old stone markers in that area documenting the level which previous Tsunmis have reached - well above the level of the power plant.
The level of paternalism and corruption needed to pull off such an act of planning is actually pretty high - Japan's culture is particularly vulnerable to this. It's the sort of thing which would be very unlikely to happen in other parts of the world, where regulation and oversight is rigorously enforced.
Taking a single incident out of context and generalising about very different cultures and different plant designs is guaranteed to lead you to the wrong conclusion.
Nobody was predicting a major nuclear accident in Japan before 2011. It makes me wonder how many other obvious mistakes are out there.
Contrary to your post, Japan has a strong reputation for safety and reliability in engineering. That kind of cultural explanations are very spurious anyway. I can come up with similar ones for many countries.
As someone living in Japan, I think this is a common misconception about this country. Just because Japanese excels in certain areas (manufacturing at scale, build quality and robustness to price ratio, earthquake safe building code) doesn't mean that it can be assumed safe in all aspects. There are a few known key areas where Japan has weaknesses. The most severe ones are IMO Software quality and lack of transparency and checks in government. The corruption induced by the latter is highly visible and failures like Fukushima aren't really too surprising knowing this. The good thing is that Japanese government is able to adapt relatively quickly when such failures become apparent - but something always has to happen first, because the chance of someone actually looking otherwise is next to zero.
And yes, this is very easily explained by culture. Specifically the culture of not questioning anyone with higher status in society. It's the downside of the importance of respect. The combination of this cultural aspect with the status of engineers being very low compared to western countries, leads to situations where management or regulatory decisions can become completely decoupled from what engineers communicate, if they even dare to communicate. If you want to solve this problem you need a rather different attack vector than the one you need in the US for example.
I find this cultural aspect fascinating. Can you please explain more about the interaction between engineering and their management? Why do you think engineering has a lower status in Japan compared to the US? Respectfully, AG
As to "what" happens: AFAIK, and that's second hand knowledge because I'm still in Academia: Engineers are the people you hire for their specific skillset in Japan. Advancement to management from these positions tends to be slow, if at all possible. This seems to be quite different from my (german speaking) home country where many CEO (and therefore also mid to lower management) positions are held by engineers. Japan has a very rigid "salary man" track system where it's pretty much predefined how old you must be and what university you must have visited in order to go on (a) a (salary man) management track for the big companies or (b) do a career in administration. Engineering is kind of separate of this whole system and generally comes with a lower overall status (and salary).
"why" is actually a hard question to answer. Might have to do with math skills being more abundant. Most certainly has to do with how the economy was modelled after WW2 (using American blueprints). Basically, imagine the way the job market in the US worked in the 50ies and then think of it as a top-down enforced policy rather than something that fell out of the need of the time. This worked very well (exceeding US growth) - until it didn't anymore, and Japan basically is still in a very slow process of adapting to the post-bubble reality. It seems like their economy was boosted so high that the bubble economy big corporations were able to survive until now and we're still in the process of getting rid of these encrusted structures. The government is certainly not helping by getting ever more in debt just to prop up dead industries. Low status of engineers, and even worse, entrepreneurs is probably one of the biggest detrimental factors to Japanese economic growth. And I really mean low, as in it is very hard to even find an apartment if you don't have a recognisable employer, even if you can show millions of revenue for your company and a high salary for yourself. Marriage market works much the same way.
I think it needs to be said that with nuclear disasters, "fault" is only passingly relevant. Blaming any one thing on the failure is irrelevant to the fact that when nuclear plants fail, they create highly dangerous and difficult to clean up messes. If an freak asteroid punctures a containment facility, it is nobody's fault, and no flaw of design, planning, etc. Yet, we still have radiation and waste to deal with.
Nuclear power is great, but it would be a mistake to ever assume it can be totally safe, and to forget that we have very little recourse when inevitable failures happen.
Net: If a power plant fails, we care a little bit about who/what/why/how, but a lot more about large quantities of lethal radiation and fallout that we have no good method of ameliorating.
But do you care the same when a filter in your local coal plant fails? That happens way, way more often and actually releases way more hazardous substances that are even harder to remove. Moreover, any stop/start of the plant likely requires oil burner start which requires the filters to be disabled (or they'd be destroyed).
Specifically, mildly radioactive ash, large amounts of smoke, sulfur and nitrites. These leach into groundwater easily (unlike fallout) and are also biomagnified like fission products.
Only natural gas is comparatively clean and there are major problems with dependency and delivery infrastructure.
(Plus it is about just as environmentally friendly to mine as coal.)
Likewise it would be a mistake to assume that it's totally unsafe based on a single instance of poor planning. But it's true that reactors of this vintage are flawed and the risks probably are too high. Fortunately we have modern reactor designs to fix that.
The level of paternalism and corruption needed to pull off such an act of planning is actually pretty high - Japan's culture is particularly vulnerable to this. It's the sort of thing which would be very unlikely to happen in other parts of the world, where regulation and oversight is rigorously enforced.
Taking a single incident out of context and generalising about very different cultures and different plant designs is guaranteed to lead you to the wrong conclusion.