Two things:
Many people died weeks and months later, even years later because of radiation sickness, long term effects...
Those where actually just two bombs, no massive bombing with hundreds of bombers and 200-1000 and more tons of bombs.
That is what basically was done in Germany as well as Japan. Really massive air raids, normally multiple air raids. And keep in mind that Japan and Germany had been bombing cities as well. So those massive air raids where probably much more normal.







