Nooo, you've got completely the wrong end of the stick.
There are always packed stadiums in Super League. RL is as popular as it has ever been and it still consistently growing, with crowd averages and playing numbers up year on year. Super League averaged over 10,000 this year. The problem is a lack of mainstream media coverage comparitive to the size of the sport(the editors of national newspapers are typical private school Union boys) and the fact that there are large areas of the country that don't know very much about the game. But overall, UK league is very healthy and continuing to grow.