Of course Rxb2 fails to Qxa8+

Exchanges help the side with material advantage of course but black has run out of play.

White now has three pawns as well as the piece and recaptures with the bishop so as to gain a tempo for defence of the b2 pawn if black is playing on.

Still no rush. Have everything where you want it before running the pawn.

Black resigns. If Rxe8 dxe8=Q Rxe8 Bxe8 leaves black with no pieces against a Bishop and Rook. A game where a black was unable to overcome the deficiencies of his opening play and not seeing the tactics by which white gained material.