In the inception stage of the community lifecycle, you promote the community to the fringe radicals, the true believers, and the people who know you best and are closest to you. These are the people with the passion to create something that doesn’t exist yet.
In the establishment stage, you promote the community to the topic enthusiasts.
These are the people who most love the unique niche you’re targeting within the broader space. They are the ultramarathon runners among the marathon runners and the bitcoin miners among the bitcoin investors.
You find them via referrals, on social media, and build close relationships with them.
In the early-maturity stage, you target the people struggling with problems, want to improve themselves, and need a better solution than what’s out there today. It’s only now that you should begin promoting the community en-masse.
There are exceptions, I’m sure, but they are the exceptions. If you’re getting lots of people joining but not sticking around, you’re probably confused about either a) where you are in the lifecycle or b) who you should be promoting the community to.