gnu, obviously you are unfamiliar with the scale of high voltage electrical grids and time needed for their repair. Because of quake damage, high voltage power cables were reconstructed from many kilometers distant from Fukushima. Heavy equipment and many electrical grid workers were involved over several days.
Pumps, relays, lines cannot be checked out until power is available and only when radioactivity is within safe limits. Connections must be tried one at a time carefully or subsidiary lines and/or equipment could be fried. That is why they started with lights and worked out (probably through checklist) connections one at a time.
Radioactivity danger to employees and resulting short working time limits complicates the re-installation.

U. S. Navy ships had backed off long before problems were diagnosed. In any case, there is no port at Fukushima reactor complex, and they would have to run waterproof cable through water, distance depending on offshore slope, to safe water depth.