He did something for the first time, something incredibly risky, with an awesome bottom line, without question, and brought the crew and the aeroplane home.
Hindsight is wonderful. At the time he was a pilot tasked to drop a new type of bomb. Nothing unusual. The boffins said it would be awesome, again nothing unusual. The whole concept of WMD and weapons which could alter the balance of a war did not exist.
So they flew a mission - a low risk mission because small formations were seen as recce missions and the Japanese air force didn't launch, keeping their assets for the mass bomber raids.
So no great shakes at the time, but notoriety and questioning fills in the past and people remember and fill in their memories.