Star Wars: 10 Things You Didn't Know About The Supremacy
5. The Supremacy Was Built In Secrecy Deep Within The Unknown Regions
When the First Order was originally trying to establish itself and grow from the ashes of the fallen Empire, the regime decided to make its home deep within the Unknown Regions. The sparsely populated areas of the Unknown Regions landed their title because of the shattered hyperspace lanes and gravitational anomalies that littered the entire region. This meant that travelling to or from the Unknown Regions was both incredibly dangerous, and vastly time consuming.
While this could easily be taken to be a negative for making the Unknown Regions your base of operations, the isolated conditions made perfect sense as a location for an evil regime rising in the shadows. Building up their armada and stormtrooper forces within the dark shadows of the Unknown Regions meant that there was little chance of the New Republic or members of the Resistance stumbling across the First Order before they were strong enough and ready to fight back.
It was only after the destruction of Starkiller Base and the First Order commencing its hunt for the Resistance that Snoke decided to step out of the shadows and unveil not just himself, but also his floating fortress in the Supremacy.