It was by no means a secret when World War Two started. The Japanese developed underway replenishment before the war. The Pearl Harbor striking force refueled its destroyers from oilers on the way to Pearl and again on the way back.
But the Japanese method could only replenish one ship at a time, trailing behind the oiler. The US Navy could replenish two ships simultaneously in 1939, one on each side of the oiler. Nimitz was responsible for that.
Nimitz was an astonishingly capable man. When you understand what he did and how he did it, it was no surprise the lead ship of the largest and most powerful warship class ever to steam was named after him.
Just a remarkable man. Great leader.