From the wikipedia article on the surrender broadcast:
As many as 1,000 officers and army soldiers raided the Imperial Palace on the evening of 14 August 1945 to destroy the recording. The rebels were confused by the layout of the palace and were unable to find the recordings, which had been hidden in a pile of documents. The two phonographs were labelled original and copy and successfully smuggled out of the palace, the original in a lacquer box and the copy in a lunch bag. Major Kenji Hatanaka attempted to halt the broadcast at the NHK station but was ordered to desist by the Eastern District Army.[2][3]
Even after two were dropped members of the armed forces still wanted the war to continue.
After the coup failed, Hatanaka shot himself. Many others did the same, and some were hung following war crimes tribunals. These people knew exactly what Japan had done under their leadership, and presumably assumed that surrender meant death.
One bomb may not have been enough evidenced by the fact that even junior level officers attempted to thwart the surrender. One bomb might have been enough. The decision to drop the second one was not entirely unjustified since the Japanese government was, apparently, in no hurry to end the war after the 1st one was dropped.
As many as 1,000 officers and army soldiers raided the Imperial Palace on the evening of 14 August 1945 to destroy the recording. The rebels were confused by the layout of the palace and were unable to find the recordings, which had been hidden in a pile of documents. The two phonographs were labelled original and copy and successfully smuggled out of the palace, the original in a lacquer box and the copy in a lunch bag. Major Kenji Hatanaka attempted to halt the broadcast at the NHK station but was ordered to desist by the Eastern District Army.[2][3]
Even after two were dropped members of the armed forces still wanted the war to continue.