In the beginning, your community is interested in the subject matter. If you love martial arts, you’re probably a member of Patrick O’Keefe’s martial arts forums.
However, over time your community should become interested in each other. You can only achieve this if you gradually shift your efforts (content and attention) away from the subject towards the members itself.
In the beginning it’s good to talk about the subject matter, but in the end it’s talking about the members that will create a true community. Shift your focus accordingly.