Stardew Valley came entirely out of left field, ConcernedApe released a pixel graphics farming sim of all things, made $35 million dollars because he’d literally done it all himself, even the game engine, and the niche (farming games) he was competing with, including games like Harvest Moon which has teams of developers pumping out absolute crap compared to what he made. Then again he wasn’t necessarily doing it to make money in the first place, it uses “timeless” pixel art, and he spent 6 or so years making the game with no actual time limit to when he could release it (as he had a day job and wasn’t going to run out of money).
And the game just has a soul that makes it feel great to play and be in. I just got around to playing it this year and absolutely love it.