The problem at Fukushima wasn't a short-term loss of coolant; it was the long-term lack of backup cooling after the tsunami hit (by which point the reactor had already been shut down for about 45 minutes), because of poor siting of the backup generators and switchgear. The operators couldn't do anything about that, no matter what they did.

Poor placement of backup systems is critical to process continuity, but in case of BWR mostly irrelevant to actual nuclear safety as long as you are willing to just write off the reactor (as you should) in case of major accident.

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.