Meh, not sure I would say that.  So here's the deal.  Two separate efforts, one more european, one more silicon valley.  The first being RDF / Semantic Web / Linked Data.  The second being Activity Streams 1.0.  Neither really got the traction they wanted.  So W3C made a WG for social with various technologies that were at a loose end.  Activity Streams was translated to 2.0 lead by IBM and with a new JSON(-LD) format.  ActivityPub was an evolutoin of the openmicroblogging, ostatus, webfinger, identica type thing.  It also came into a linked data world, but not 100%.  ActivityPub was based on LDP inbox, which was before it solid inbox, which before that was semantic inbox.  Semantic inbox was simply the idea of doing email but with HTTP and rich data.  ActivityPub added an outbox (which turned out to be critical as it validates data), followers and activity streams.  Then Eugen came along and made a stunning interface which made it take off, before that there was very little traction.  The link to FidoNet I think is a bit tenuous.  It's 2 world coming together because they didnt do as well as they hoped, and then a viral implementaion came after.