What was "one of the most important decisions of the battle of midway

The answer is that the pilots decided to proceed to a secondary location, and they found and attacked Japanese carriers.

Instead of returning to base, aviators made what Admiral Nimitz would later call "one of the most important decisions of the battle."

The pilots then proceeded to an unlikely secondary location. There, they found the Japanese carriers - unprepared. Immediately, fighters destroyed one of the four Japanese vessels. Other Americans rushed onto the scene to continue the attack. This event shifted the tide of battle to favor the Americans, wresting victory from Japanese hands.