It's, ironically, a case of the "embrace and extinguish" philosophy that Microsoft was reviled for.
I remember reading posts by several people which said they weren't going to build a RSS reader because they didn't want to compete with Google Reader.. and then they went ahead and killed it.
RSS didn't really "take off" with mainstream users (I guess today's equivalent is Twitter), but it filled an interesting niche.
RSS -> Twitter
Usenet -> many proprietary platforms
IRC -> Slack
XMPP never took off
Many open, interoperable services died off or never took off, but companies built similar services and are enjoying success.