The history on this is pretty sound ... a major bombing campaign was started much earlier to avoid any invasion or boots on the ground.

Seventy two Japanese cities, including Tokyo, were already completely destroyed before the two atomic bombs were dropped. The two cities destroyed by atomic bombs were on a list to be destroyed regardless.

To the people killed, injured, or left in the shell of a city with no food or water it made very little real difference whether the cause was HE+incendiaries OR high burst shockwave from atomic bomb - the M&M statistics (death and injury, both immediate and following) were similar in either case.

The greatest military imperative to drop the atomic bombs were pragmatic .. they were developed at vast expanse for use on Germany but were not ready until after Germany surrended .. to close off an R&D program without a live target test on targets already targetted for destruction just seemed ... wasteful.

After the bombs were dropped, everything changed. Public awareness and perception. The need for post war PR. The start of the Cold War race with soviets over atomics. The pressing need for auto biographies and centre staging from actors late to the story, etc.

Much of the "justification" for dropping atomic bombs was retconned after the fact.