The US intention was clearly to commit mass murder of civilians (most of them members of the working class): They threw the bomb in the city center, not in the few nonstrategic military barracks nor in the military industries, and less than 10% of the deaths were militaries.
See, by example, https://www.lawfaremedia.org/article/hiroshima-and-myths-military-targets-and-unconditional-surrender
Hiroito was never judged by those crims. I suspect that fight against fascism was not, and never has been, a priority of the U.S.