The whole "sovereign citizen" thing started in the fringe of the tax protest movement. Declare yourself an independent sovereign citizen and the US government no longer has authority to tax you.
Now it seems to have managed to degenerate further into a cover for scam artists. They probably are figuring if they can move into the house, file anything with the courts and manage to stay in the house long enough to establish some history and a paper trail, they can turn around and sell the house.
Jay