dAGGER: I think you can safely assume the majority of the players are aware tournaments exist, that they can sign up, and furthermore, that there are boards for each (group of) games.

I also think there the number of different people posting on boards is much smaller than the number of players - no doubt many player don't read (all) the boards because they just want to play, not read or post.

I think you have to face the possibility that Espionage just isn't that popular. Just over 13 thousand games have been played - counting all five variants together. That's less than a far more recent game like Knight Fight, which, without the benefits of variants, has more than 18.5 thousand finished games. And it's utterly dwarved by the number of Backgammon matches whose count stands as of this moment at 861957, 65 times as many as all the Espionage variants.