Deeper Blue played 28. .. f5 "instantly", according to media reports.
Morely likely it got suckered--the track record clearly demonstrates that
computers snatch material with no regard to the deeper consequences.
At this point it "believes" that it is on its way towards winning a rook
at the mere expense of bishop and pawn.
The machine's win of the minor exchange was at the cost of the game.
White carried the day with his well-placed bishop on c3, small pawn steamroller,
and mating nets which exiled and finally consumed the Black king.
31. .. hg was not possible, as White then opens a line for his queen
with 32. Ng4! Bxg4 33. Qxg5+ and mate to follow.
Further, this game has a minor theme: Black's aggression on his second move
(2. .. Bg4) marks the square of his demise: 22. .. g4?!, and Kasparov's
predictably winning 39. g4!