In order to swap the defender on c6.

A tempting sacrifice to intensify the attack;

Black overlooks 5...Qd5 6.Qb6 Rxe4 , when White has to settle for a draw by 7.Bb5 , followed by Qa5-c7-a5.

Black resigned.

Swapping the main defender of Black's kingside.

Now that Black's dark-squared bishop is gone, this knight cannot be exchanged.

This quiet move connects the rooks with decisive effect.

Black resigned in view of 5.Ke2 Qxc3 6.Qxc3 dxc3 7.Rah1 and the mate is inevitable.

Eliminating the main defender of Black's kingside.