[pdonis]

> In such situation just leaving the reactor be would cause destruction of the reactor and no major environmental impact

I'm not sure the last part is true; as I understand it, there was a significant risk of a containment breach if decay heat removal was insufficient--not from the reactor cores themselves, but from the spent fuel pools.

I agree with you, though, that any attempt to save the reactor itself was doomed to failure once the tsunami hit and the backup cooling was taken out, so any actions taken toward that end were misguided.