For whatever reason, the Alliance has ended up with a few player groups whose goal is Alliance expansionism in the general sense, and which are less attached to specific factions, while the Federation and Empire don't really seem to have that - possibly because the players who would are instead focused on the Fed/Imp conflict in Powerplay?
So as with the Marlinists today, the Fed/Imp WH factions didn't really have any significant number of "natural" supporters.
(And it'll be interesting to see, if Frontier do develop either the Marlinists or Kumo into a more significant political entity, whether they attract more baseline supporters in that sense, and what it means for the story if they don't)