Lightning from a clear sky.
More complicated but possible was 17.Qxa7!? Nc6 18.Qa8+ Nb8 19.a4! Bd6 20.a5 Qc6 (20...Bxg3 21.a6 c6 22.Bf5+–) 21.Bh4! Ne4 22.Bxd8 Rxd8 23.a6 b6 24.Qxc6 Nxc6 25.Bxe4 dxe4 26.Rxe4, with the advantage in the endgame; But nothing was achieved by 17.Bb5 c6 18.Qxa7 cxb5∞.

Losing at once. But even after the strongest continuation, White keeps extra material:
A) 18...Qd7 19.Qxa7 Qd6 (19...Qe8 20.Rae1 Ne4 21.Qa8+ Kd7 22.Qxb7 Nd6 23.Qxd5+–) 20.Rae1 Bf8 (20...Qa6 21.Qxa6 bxa6 22.Rxe7+–) 21.Rf5 Qc6 22.Bh4 Bg7 23.Re7 b6 24.Bxf6 Rde8 25.h4±;
B) 18...Qg6 19.Rxe7 Rd7 20.Rxd7 Nxd7 21.Qxa7±.

If we exchange the Bf7, Black recaptures with the rook. The diagonal remains partly closed, and White cannot exploit it. Therefore, White carries out the exchange on another square, exploiting a tactical motif:

First, White lured the enemy queen onto the desired diagonal, and now he deflects her from it.

The white knight quietly returns to the centre, and the e-pawn, supported by its pieces, proves decisive.

Black resigned.

The black king is in danger. The f7-square looks inadequately defended, and the set-up Qh7-h8 and Bb1-h7 is crying out to be played. However, the Nf5 prevents this, and after the straightforward 27.Qh8, there follows the simple 27...g7-g6. A nice tactic comes to the rescue:

In the game, White did not find this move, and after 27.Rd1 Qc6 28.Qxg8+ Kxg8 29.Ne7+ Kf8 30.Nxc6 Rxc6 Black managed to save this difficult endgame.

In the event of 27...Qxe7 28.Rxe7, White has a decisive material advantage.

And Black is mated.