Another example I can think of is the Minecraft wiki, which originally was its own thing, but through a series of acquisitions ended up with Gamepedia/Fandom.
"On September 24, 2023, after growing frustrations with the Fandom platform, the wiki completed its process of moving from Fandom and is now hosted independently at minecraft.wiki by Weird Gloop, with the old Fandom wiki now deprecated. The move also re-introduced a skin similar to the one used on Gamepedia, re-enabled anonymous editing, and introduced a new logo."
https://minecraft.wiki/w/Minecraft_Wiki_(website)
The most active users split from it and created https://minecraft.wiki/
"On September 24, 2023, after growing frustrations with the Fandom platform, the wiki completed its process of moving from Fandom and is now hosted independently at minecraft.wiki by Weird Gloop, with the old Fandom wiki now deprecated. The move also re-introduced a skin similar to the one used on Gamepedia, re-enabled anonymous editing, and introduced a new logo." https://minecraft.wiki/w/Minecraft_Wiki_(website)