The success of this gambit against Zarahemla encouraged Coriantumr to continue. He thinks to run a line from Zarahemla down the Sidon valley, and on to Bountiful. Capturing this central corridor would split the Nephite forces that were on the east and western peripheries, and rip out the heart of the land from them – quite literally. Coriantumr likely planned to deny the outlying Nephite armies the provisions that might have come from the supposedly well protected interior. With the army split, and the main support system destroyed, Coriantumr would be able to so weaken the Nephites that their government would collapse. At least this is the probable thinking that drives Coriantumr’s next actions.
He takes his force and continues the blitzkrieg down the valley. The Nephites have still been unable to get the word around to call the men to arms, and so Coriantumr is still fighting light and perhaps unorganized resistance in his march down the valley.