The first city mentioned is Zarahemla. Although others are listed somewhat by region, Zarahemla is first, and not in the same region as Moroni or Moronihah. It is mentioned first because it was the “first city” in terms of conceptual importance. It was the capital and, therefore, the most important city. It was burned. If Zarahemla were no more, then the Nephites would understand how great the destruction was, even before the rest of the cities listed.
The city Moroni was already mentioned as having been sunk in the sea, but that was an account written after the fact. For most of the people, they learned of that disaster through the voice of God, which made it more terrible.
God’s power over nature is emphasized by the symbolic death of the cities, being buried in both water and earth. If that imagery were to be understood, then the fire of Zarahemla might also have been symbolic of the burning of the wicked in the great judgment.