i think i dont understand what stockfish does then. doesn't it play the basically perfect move at each step? how is it possible to beat stockfish 70% of the time? with a naive GPT type thing?
"the basically perfect move" has a lot of implications here.
Because chess isn't a solved game a seemingly "perfect move" in a game involving two 2000 ELO rated players might not seem perfect to a 3000 ELO rated player. (To be clear: the only actual perfect moves are ones that all trees lead to a checkmate, but in general use "perfect move" means roughly the best possible move to play)
In this case Stockfish was set to a lower setting which corresponds to 1320 ELO.