This analysis is masterful; I congratulate you.
I’ll contribute a bit from my experience with two different audiences. For both, we have the support of Appreciator, so no one who joins us is left without a vote.
With Hive goes to School, it has been an immense task. After the first post, they don't want to continue; they don't like publishing and they discovered that the subject doesn't carry an academic grade 🤣. At first, they are excited about earning money with their classes—something unique and disruptive—but then they get bored; they don't want to write 300 words. Most don't even withdraw their rewards. So, rewards are not the determining factor. They are 16-year-old kids. You can see them here.
The other case is Hive Run. I could swear it’s among the top 3 communities for retention—maybe even the first—though I haven't done a detailed analysis yet. It is even very good in terms of HP (Hive Power) retention.
We have Appreciator votes on weekends, which is when most people post their training summaries. However, several also post during the week.
What I believe differentiates this community is:
I have often said that the key is for niche communities to do onboarding for their specific community, not for Hive as a whole, and for whales to support that.
In this sense, and since you mention OCD—which has or had the community support program—it was missing the piece of external promotion by those communities, because they always got used to attracting already active Hive users and no one from the outside.
Now it seems OCD has shifted in another direction, as for months it has reduced author rewards to dedicate more to POSH. It would be good to analyze the results of POSH and if that reduction in rewards has influenced retention.
RE: The Single Most Impactful Thing You Can Do For Hive: Upvote a Newbie