Key difference is that Bitcoin people want/need their numbers to go up,up,up as a measure of success.
Here, we are hoping to cultivate a healthy community (at either/both the instance and fediverse level). From my experience on various subreddits, focusing on growth is not a good way to do this.
Communities are defined more by who is not allowed in than by who is in the community. Lemmy phase 2 kicked off back in June, and it still needs some time to find its footing at a sustainable rate of growth.