Please someone explain me why/how Google Groups have some posts predating the Internet? Were those from message boards on primitive forms of network like the Minitel?

Technically the Internet has been around since the 60's in one form or another and Usenet existed since 1979 or 1980. Google Groups simply archived old Usenet messages dating from 1981 to present. It's a common misconception that Internet has started existing in 1995 because that's around when the first big websites and web browsers started appearing.

I knew about ARPANET, Usenet and stuff, but wasn't that stuff used for research / military usage only? I thought it was with the popularization of the internet that those networks started to be used outside that range, hence why I'm surprised about that hockey necropost.

I have seen logs from usenet discussion, for example those in which Torvalds announces he wrote a basic OS for Intel 386 processors (Which later became Linux), but those are usually programming or research oriented.

I knew about ARPANET, Usenet and stuff, but wasn't that stuff used for research / military usage only? I thought it was with the popularization of the internet that those networks started to be used outside that range, hence why I'm surprised about that hockey necropost.

I have seen logs from usenet discussion, for example those in which Torvalds announces he wrote a basic OS for Intel 386 processors (Which later became Linux), but those are usually programming or research oriented.

I have the feeling that mailing lists became mainstream in the 80's, which probably explains why Usenet was popular back then. HTTP, on the other hand, only arrived in the mid 90's.