An approach for growing a high-engagement ecosystem.
You want low engagement users to not even think about the ecosystem until there is so much vibrancy they'll be high engagement, because there will be something happening they care to participate in.
A lame ecosystem is one where there are lots of people just standing around.
All of those people watching put a chilling effect on the people creating.
If you have a big splashy PR or marketing driven influx, then most of those new people will be low engagement.
They come, see everyone standing around awkwardly, and leave, never to return.
But if you can make it so the next person to join is the next most motivated person, you can have a high-engagement ecosystem that continually pulls in lower engagement people who will now be high engagement as the momentum and vibrancy picks up.