White cannot afford to let the a5 pawn drop, as this would give Black a third passer; so, the White Queen must come out of her lair to defend the a5 pawn, giving Black the opportunity to trade off a critical defender. 35. Rxb2, QxRb2; 36. RxQ, RxR; followed by ... Ra2 picking up the a5 pawn would favor Black.
White has defended tenaciously until now, but here he relaxes: 40. Kf1 offered stronger resistance; the threat of ... Bc3 could then be answered by 41. Ke1 so that after ... BxBd2 White could retake 42. Kxd2 and maintain the blockade of the d-pawn. White's position would nonetheless remain almost completely paralyzed and White would be unable to prevent the Black K from penetrating the position.
40... Be5c3
This breaks the blockade on d2, after which White can no longer stop the d-pawn. The sequel might have been: 41. BxBc3, RxBc3; 42. Rxb2, RxRb2; 43. RxRb2, Rc2; 44. Rb1 or Rb3, d3-d2 and the d-pawn is home free. Note that if the Black K were on g8 here, then White could hold the position with 44. Rb8+, Kf7; 45. Rd8, d3-d2; 46. Kg2. But with the Black K on f8 instead, 44. Rb8+, Ke7, the White rook cannot occupy the d-file to stop the d-pawn. White resigned 0 - 1