It’s hard to claim the nuclear bombs were a major contributor to their surrender when Japan was trying to surrender before the first bomb dropped

They had a minority interest in surrendering before the first bomb dropped. The Fire Bombing of Tokyo civilan centers (arguably a worse atrocity than the bombs) had their morale and their communications broken, but every source I've ever read concludes that they genuinely were not ready to surrender, and it would have taken an actual mini-coup to do so, one that seemed to not be happening.

That doesn't mean the bombs were necessary. They were, however, contributors to the surrender. The Japan preparing to rally from having their capital razed, civilian targeting worse than they had seen either side commit in the war, was suddenly struck with Hiroshima being vaporized.

I DO believe they were in the process of surrendering when the bomb hit Nagisaki.

Taking a step back, the bigger question is whether there are wrong ways to win a war. The US took Japan to surrender using 4(or more?) of the biggest civilian-targetting mass-death events in human history. We destroyed their civilian economy with lethal force in preference to destroying their military infrastructure. I think that was unacceptable.

But it DID contribute to the surrender.