The comment that the war was “swift and speedy” is the reason that “there was none left to bury the dead.” Rather than stopping the war to perform rites for the dead, the destruction continued, and the dead were left on the land. It is possible that the conquering army did bury those of their own people who had died, but this devastation was certainly committed upon the enemy.
Sadly, Moroni would have been all too familiar with “the scent thereof.”