This is narrative that Mormon is writing, rather than a text he is copying. Therefore, when we see the parallels to the great destruction in 3 Nephi, we must understand that the parallels are intentional. Mormon is setting up these conditions as preludes to both a miracle and to the declaration of a prophet, or of God coming to earth in 3 Nephi.
Most important is the voice from heaven, speaking after the cloud of darkness and the destruction. Mormon spends several sentences on this part of the event, making certain that his readers would be able to associate this miraculous event with the one that is coming in 3 Nephi.