In my experience, the result of bad decisions is usually due to incomplete information and risk assessments, whether by an engineer or management. Management usually has more risks to balance than the engineer. Engineers are typically only concerned with technical risk while management has both technical and programmatic risks to balance. When the balance tips towards programmatic risks, it may be due to a poor understanding of the technical risks as well as a bad incentive structure. When the technical risks aren't well understood, it's generally not because management is too dumb to grasp it. It's more likely the culture and organizational structure don't foster good communication or accurate assessments of those risks. For example, if you look at the Challenger disaster, neither the engineering staff or management has great estimates about the risk. (However, the engineers were much closer to the true risk probabilities). It came down to a concrete schedule risk vs. a somewhat nebulous technical risk and the absolute risk won out in the management decision process. In your Fukushima example, I'd bet the "idiot" probably didn't have an assessment (in terms of a failure-modes-effects-analysis or hazards analysis) to properly gauge the risk of their action. (Or there were likely communication failures of that risk, or both.)
I think the important point is that to really fix these issues, they have to be addressed as part of a process failure rather than pointing fingers distilling it down to a simplified notion that it's somehow the fault of an "MBA mindset"
You will note that I specifically chose the spraying of water at Fukushima as a management failure (we can argue about the lack of failsafe for the cooling ponds)--because some idiot counting dollars decided to try to "save the core" they caused a hydrogen explosion which made things orders of magnitude worse.
In both Fukushima and Three Mile Island, for example, if everybody had simply SAT ON THEIR HANDS AND DONE NOTHING, the situation would have turned out far better than it eventually did. Yes, the Fukushima core would have still melted down, but it wouldn't have sprayed radioactive material all over the place.