This was the idea that Duanmu Huai proposed to King Gandhi.
Although King Gandhi's control over the civilian officials was weak, luckily, the military was still firmly under his control. When King Gandhi first mentioned the Demon Clan's invasion of Lisas at the early council meeting, it was to set the tone for the ensuing proposal, turning it into a "military task".
Military tasks are entirely different from political ones, and the concerns King Gandhi had indeed existed. Under these circumstances, constructing a satellite fortress city in the heartland that echoes the Royal City is indeed a pressing military task.
The reason Lisas suffered so much at the beginning was that most of Lisas' armies were on the border, and no one ever thought that the enemy would bloom in the middle. When the Herman Soldiers launched their attack, Princess Leia had nowhere to run but to surrender.
After all, who could anticipate that kind of situation, right?