It's obvious isn't it? He might care because it takes them towards financial sustainability (though I doubt it makes much of a dent), but it's principally about trying to establish an element of moral legitimacy? If they have the biggest crowds it can be spun that "the best-supported club won the League because" rather than "the best-bankrolled club won the league".
Funny how the Leatherhead comment, being straight from the Maureen playbook, undermines that a little.
And I think we can be less touchy about his name-check of us. Saying "I want our crowds to be bigger than Dulwich" is just shorthand for "I want our crowds to be the highest in the League". It saves a whole syllable!