bc he's higher rated
Rating bug

Like AlgebraicGamer and Nathankuonat suggested, I believe those rating estimates are skewed by the actual rating of the player. If you had played the exact same game against an 1800-rated player, their estimate might have been 1500-1600. The icons for Opening, Middlegame, and Endgame must also be affected by the player's rating. You played a great middlegame for a 1200-rated player, and your opponent played a good middlegame for a 2400-rated player.
I recently reviewed a game between me and a FM. I lost, and when I hovered over the rating guesses from chess.com, it said in the middle game I had a better performance than my opponent based on the symbol. However, my actually accuracy in the middlegame was lower. Why is this? The link is: https://www.chess.com/analysis/game/live/5085539604?tab=review