My opponent played scissors in round 1, which beat my paper. Players often stick with a winning move, so there's a chance they might play scissors again. If they do, rock would be a good counter. Additionally, after winning, players sometimes switch to the move that would have beaten their previous choice (paper in this case), so rock also beats paper if they make this strategic shift. Since I'm already behind 0-1, I need to make a strategic choice with higher probability of success.