The powers that be and the military were dug in. There was nothing left from the normal bombing to bomb. Just nuking rubble and starving people.
Someone may be able to post a pic of Tokyo at the end of the war, no nuke and still no city.
Think of it from our day perspective, we are not that fanatical, but do you think the USA, UK, USSR would surrender because they were threaten by a nuke attack, or had a few cities wiped out. No they would have kept going to the bitter end and civilian casualties would be way down the list of priorities. Jim