Japanese civilians, in many cases, were absolutely victims. The Japanese government? Japanese society? Not a chance. They set out to do a colonialism like many other imperial powers during that time and they reaped what they sowed ultimately.

The nukes weren't even the worst thing the US did to Japan. The fire bombs killed more people and destroyed more stuff. The nukes were just a shock. A sustained bombing campaign is expensive and risky to trained personnel, but if all it took was a single bomb to take out a large city, then things changed. Suddenly, the US could wipe out the Japanese population in a month or two, rather than years of bombing campaigns followed by costly ground invasions.

As the reasoning behind the use of the nukes, well the standard explanation is that they would it would be expensive to bomb the Japanese into submission and it would have taken 1M+ American troops to do the job ultimately. This explanation works on paper, but the likely more important explanation was the US was worried about the Soviets getting into the war with Japan and claiming it for their own. The Soviets were much more willing to throw people into the meat grinder, and Japan would have been a meat grinder.