There was no IM standard at the time. Every provider had their own standard and most of the IM software was not open sourced. Jabber changed the playing field.
Changed it how? Google has since tossed XMPP integration for their whole closed platform Hangouts thing, MSN's old halfway-API-able thing has been integrated into Skype, which is entirely closed, I believe. AIM and YIM are all but dead, at this point.
