Etienne Wenger wrote long ago about the importance of an agreed domain of knowledge.
He referred to communities of practice, but I’m sure it extends beyond that.
In every online community, there is knowledge people are expected to know. There are also upcoming questions. What’s new? What’s going to be the next big thing? What’s changing?
These are the questions that cause tension and conflict for many communities. They create difficulty for many people. They are also terrific for stimulating a lot of activity.
It’s these questions you can use to build a community around. You can identify untapped niches. You can host events/discussions/polls around them. You can invite experts to talk about them. You can further develop the community.
It’s great to truly understand the domain of knowledge, but it’s even better to know where the cutting edge lies. Make sure your community properly lives in that space.