The reason why the commercial district was spared from the influence of the factions and powerful figures was not only because it provided a substantial tax income to the city, but it was also because the commercial district was a window for all the major factions of the world to get in touch with Darkness Port.
The majority of businesses in the commercial district belonged to the major factions that had settled down in Darkness Port for a reason that was fairly easy to understand. It was the only safety city by the shore and was blessed with rich aquatic products.
If Darkness Port did not take a step back and allow the other factions to have a piece of the pie, it would become the target of the world.
However, it was obvious that Darkness Port did not want to simply compromise, hence the city opened up the commercial district and allowed the major factions to settle in, forming a subtle balance between power.