Fischer vs Sherwin Game - 1957 In this game Move # 32 Sherwin play Rxh7 and this move makes him lose the game, so why he didn't play Rxf6? is this mistake from him? or something I didn't get.

[FEN "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"]
[White "White - Fischer Robert J (USA)"]
[Black "Black - Sherwin James T (USA)"]

1.e4 c5 2.Nf3 e6 3.d3 Nc6 4.g3 Nf6 5.Bg2 Be7 6.O-O O-O 7.Nbd2 Rb8 8.Re1 d6 9.c3 b6 10.d4 Qc7 11.e5 Nd5 12.exd6 Bxd6 13.Ne4 c4 14.Nxd6 Qxd6 15.Ng5 Nce7 16.Qc2 Ng6 17.h4 Nf6 18.Nxh7 Nxh7 19.h5 Nh4 20.Bf4 Qd8 21.gxh4 Rb7 22.h6 Qxh4 23.hxg7 Kxg7 24.Re4 Qh5 25.Re3 f5 26.Rh3 Qe8 27.Be5+ Nf6 28.Qd2 Kf7 29.Qg5 Qe7 30.Bxf6 Qxf6 31.Rh7+ Ke8 32.Qxf6 Rxh7 33.Bc6+  1-0
Because the rook on b7 is en prise. It is attacked twice (by the rook on h7 and the bishop on g2) and only defended once (by the bishop on c8). Either way the game is lost.