@jeffcliff @brainblasted The chronology rather goes the other way. Diaspora's growth stagnated before they lost their lead dev.
I think a lot of it is the curse of great funding, and very enthusiastic people taking on a bigger project than they realized. When the funding ran out, the project lost steam.
Alternatively, one could say that the Diaspora Federation is alive and well, and the people in it are happy, feel that it is a success, and don't really feel the need to take over the world.
It's very encouraging to see that new projects are popping up around Diaspora lately, and that e.g. #socialhome is aiming to support both the Diaspora protocol and ActivityPub.