Their only condition was that they wanted to keep the Emperor. It was ridiculous of the Allies to demand a wholly conditional surrender. All those people got blown up just to win the argument about that one point. They could have ran a conventional air bombing campaign against tactical targets, but they decided to drop nukes on a "tactical" target in the middle of a huge city! And then they did it again! That's not tactical, that's strategic. If you're going to use nukes, at least use them on a military base far away from cities.

What made the Japanese surrender was the Soviet Union declaring war. They held out hope until the very end that the soviets would mediate a peace, even after the nukes.