The fire continued ravaging the Flesh Golem for a little while, but it eventually died out after making the Golem use incredible amounts of demonic energy to restore its flesh. Toz wanted to continue with the fight by taking advantage of when the Flesh Golem had been occupied with the flames, but he had to do something else first. He had to lose the baggage that was limiting his movement.
After setting the Flesh Golem on fire, it and the Death Knight were naturally interested in killing him. However, they weren't so free that they could freely chase after Toz as he skirted around the edge of the battle to catch up with the retreating Alliance of Kingdoms.
Since the mana storm had started nearing their battle, the Alliance of Kingdoms knew that they wouldn't be able to do anything. And instead of needlessly trying to endure the storm just to see the three giants fight, it would be better to fall back and see if the mana storm continued their way.
