The B-29s dropped white phosphorous, napalm, avgas, etc in specific patterns intended to create a firestorm -- a phenomenon pioneered by the British in places like Hamburg and Dresden. The flames were so intense that subsequent waves of bombers were lifted in flight, and the glow could be seen for hundreds of miles. Over 100k are estimated to have died. A million+ were homeless.
This isn't something that was covered up/deempathized, nor was the atomic bombing. Obliteration of the enemy from the air was heralded during and after the war.
Far from covering it up, this kind of thing was a massive boost to the career of Curtis LeMay, the man later charged with commanding the Air Force's nuclear arsenal as commander of SAC.