Other good examples: Linuxthreads to NTPL (for providing pthreads), XFree86 to Xorg.
I was using Gentoo at the time, which meant recompiling the world (in the first case) or everything GUI (in the second case). With a strict order of operations to not brick your system. Back then, before Arch existed (or at least before it was well known), the Gentoo wiki was known to be a really good resource. At some point it languished and the Arch wiki became the goto.
(I haven't used Gentoo in well over a decade at this point, but the Arch wiki is useful regardless of when I'm using Arch at home or when I'm using other distros at work.)
Arch was young in those days but I think fairly well known? we were quite vocal, opinionated and interjecting our views everywhere by the time of the Xfree86/Xorg switch. Perhaps it is just my view from being a part of it but I remember encountering the Arch reputation everywhere I went. Or maybe it is just the nostalgia influencing me.
I'm on Gentoo without the precompiled packages, except for very large applications. Gentoo wiki is not a match for Arch wiki for its sheer content and organization. But Gentoo wiki contains some stuff that Arch wiki doesn't. For example, what kernel features are needed for a certain application and functionality, and how a setup differs between systemd and other inits. I find both wikis quite informative in combination.