It’s one way communities can grow. Especially in lower population forums, it makes sense to start out more general to concentrate enough traffic instead of spreading it out into a bunch of mostly dead, niche communities that fail to hit the critical mass required to get people coming back and posting more. Once the community has grown enough to the point where a certain type of content is drowning out the rest, that content gets separated off into its own subforum or community. You’re seeing it as a mistake to avoid repeating, but it’s actually a great benefit to both this community and the future communities that will eventually spin off.