That's not necessarily true. Jabber was a huge protocol already and IRC was big too and those were not about brand names. Jabber was even so ubiquitous that Google Chat/Talk both used it as a backend. You could add Google Chat to any client that supported Jabber. It wasn't until AOL got wind of AIM being a way to grab more ads and cash that things changed.
Twenty years ago was the year 2000. Trillian first shipped as freeware that year, and shipped its for-pay "Pro" version in 2002. Jabber/XMPP development only started in 1999, and didn't reach RFC status until 2004. Google Talk didn't ship until 2005, and didn't support federation until 2006. The heyday of "XMPP all the things" was from 2008-2012 or so, with the high water mark being the adoption of XMPP by Facebook Chat circa 2010. (A decision they eventually reversed a few years later.)
IRC was of course always open, but that's kind of orthogonal to this discussion as it never really had any traction with the general public the way AIM, ICQ, Yahoo! Messenger, etc. did.
