To be fair, the !StatusNet network that Evan was running became unmanageable -- it cost too much to run, and I think Evan was funding most of it himself (although there were/are a number of paying #StatusNet customers). Evan developed #PumpIO to reduce the number of servers needed to run a federated network, and purposely kept the UI to a minimum to encourage federation. Sadly, that didn't work. Porting identi.ca from StatusNet to PumpIO was intended to introduce people to PumpIO as well as reduce Evan's costs. That partly worked; identi.ca is alive and well as a community, although much reduced from its glory days around 2013. But the #bifurcation did spawn a large number of new StatusNet / !GNUsocial instances, so that was a good thing too. But you're right in that PumpIO never gained widespread traction, the proof of which is in its lack of continued development. In that respect #GNUsocial and !OStatus are more successful than PumpIO