There's a description of the latter I've spent far too long trying to track down without joy.
There's a passage from Charles Perrow's book Complex Organisation giving several examples of organisational drift (not necessarily decline), posted previously: <https://news.ycombinator.com/item?id=27415476>.
One of the more spectacular cases of organisational decline was the (formerly literary) magazine American Mercury, founded by amongst others H.L. Mencken. It eventually became an anti-semitic rag, now mostly or completely dead, though it seems to keep zombying annoyingly.
<https://en.wikipedia.org/wiki/The_American_Mercury>
There's also video challen TLC, begun as a partnership between Nasa and PBS, now somewhat reduced as well.
Before there is a subculture, there is a scene. A scene is a small group of creators who invent an exciting New Thing—a musical genre, a religious sect, a film animation technique, a political theory. Riffing off each other, they produce examples and variants, and share them for mutual enjoyment, generating positive energy.
The new scene draws fanatics...
I've mentioned that previously on HN as well as the Fediverse:
My experience: the only way to stay good is to stay small and exclusive, but the internet attacks this defense directly and destroyed it, and at the same time destroyed itself. You need to find the "golden age" of all these systems, enjoy them while you can, try and protect them but recognize their transient nature, and then aggressively cull and move on. Hold onto values not manifestations.