I love that a service that isn't making a buck off of us gets levels of engagement that for-profit social networks would kill for.
This is happening because:
Novelty, because new is fun. This will go down over time.
The most passionate users are more likely to be early adopters. More casual users are coming.
Smaller network means your content is less likely to be covered before. This factor will go down over time.
Fediverse encourages multiple related communities, which means your specific contributions are more likely to be seen by other users.
Lack of bots/astroturfing leads to more positive interactions. Bots will likely increase over time.
Therefore, I expect engagement will go down over time, but I am hopeful it will reach a higher point of stability because the fediverse design seems better at getting more varied content seen by its users, and it makes it harder for a small group of people or posts to dominate the discussion space.
PS: Anybody know how to add a space after the last bullet in a list?