I thought ConcernedApe was a solo dev.
StardewValley
For lovers of Stardew Valley, the coziest video game ever!
He was, Stardew 1.0 was entirely his work and he worked on it for 4.5years. Other developers were brought in to help with porting to other platforms and for the post 1.0 point releases, but the team sounds like it remained small. For 1.4 and 1.5 it sounds like a two person team for example.
Something about other devs and bug fixes and localizations I think?
Common misconception. He started development solo, but quickly found he needed help from other development teams.
Not that quickly, Eric Barone worked on the game by himself for over 4.5 years. Version 1.0 was entirely his work. He only brought in other people when the game was ported to other platforms and for the later point updates.
Arthur Lee contributed to the 1.4 and 1.5 releases of Stardew Valley. He's also aired his greviences about being hired as a contractor on the game but then wanting and not getting a profit share for future projects.
It's my understanding that he picked up a team for ports to other platforms and networking. Since then, they now work on all aspects of the game, but Eric still has final say.