I mean

There were networks such as: EFnet Undernet Quakenet DALnet

different servers in different regions did network together.

There was a different word for ‘defederation’ back then: net split https://en.m.wikipedia.org/wiki/Netsplit

And it was usually from a networking issue.

I’m still salty that an IRCOP from a (now defunct) Canadian server used a net split as an attack: https://en.m.wikipedia.org/wiki/IRC_takeover

to steal a # channel from my friends and make it private long enough to sort out the bot auto bans. We appealed, but because they were an IRCOP, the other IRCOPs from the federated servers were just like, “whatever, pound sand users, go run a server if you want to control stuff like us.”

Anyway, IRC was a connection of various servers run by various people/corporations/universities etc.