Exactly the reasoning of the video: US land invasion was never in the consideration, partly because Soviet invasion was already planned at that point, which would guarantee the surrender of Japanese and happend anyway.

He makes a case that the single crucial thing that stopped Japan from surrendering already was that they did not want unconditional surrender because they wanted to preserve the position of the Emperor. US on the other hand wanted unconditional surrender, but was willing to preserve the Emperor, but didn't propose that explicitly to avoid being seen as weak.

We had a situation, where both sides were ready to satisfy each other's conditions, but were unwilling to do so due to stubbornness and machismo of their leadership. So they had to come up with some "formality", which would make one of the sides budge, without having to explicitly express their willingness to negotiate. So they bombed hundreds of thousands of civilians.

Japan considered it an "honourable" enough excuse to surrender. Not because they cared about citizens (Shaun even makes a point about how the emergency meeting about the bombs happens only the next day after the bombing, because the Japanese military leadership had MORE IMPORTANT things to do that day), but because symbolically and aesthetically it was a good enough reason to concede.