Before leading the Fleet to clear the Demons on the West Bank, Rocky had already given orders that after his departure, Thunderhawk City would head directly to Red Water Lake. At that time, his idea was relatively simple, wanting Thunderhawk City to land on the West Lake Shore and complete its upgrades.
However, as he encountered a large number of high-level Demons during the clearance process, later met with the Fireteng Tribe, and finally went to the Cave of Blood Cries, amid this series of events, he had essentially abandoned the plan to upgrade Thunderhawk City here, simply because it was too dangerous.
But since everything had happened so suddenly, Rocky hadn't had the chance to issue new orders to Thunderhawk City, and so the city had already arrived.
In response, Rocky didn't seem too concerned, because even if it had arrived, there would be no problem as long as it didn't land.