If you're seeing it and you're not subscribed here there you must be browsing Local or All rather than your subscribed communities.
- Subscribed - only stuff you're subscribed to (called Home in some apps).
- Local - all posts from communities on your instance, and this Stardew Valley community is on your instance.
- All - all posts your instance knows about, everything from your Subscribed and Local feeds plus every post from every community that someone on your instance has subscribed to, including communities on other instances
So the answer is that you're seeing a lot of posts because someone is making a lot of posts, people are upvoting them (the game is from 2016 but it's still very popular and still getting new content updates) and you're viewing feeds where they show.