The black kingside has been abandoned to its fate by the black pieces:

Black resigned. Wherever the queen goes, she comes under attack: 20...Qb8 (20...Qa7 21.Nc6+–; 20...Qb7 21.Ne6+–;
20...Qc5 21.Ne6 Be5 22.Bxe5 dxe5 23.Nxc5 bxc5 24.Nc7+–) 21.Nc6 Be5 22.Nxb8 Bxb2 23.Nxd7 Bxd7 24.Nxb6+–.

White has sacrificed a pawn, and needs to show that he has something for it.

An unexpected square for the queen. The main idea is to cover the square e3, via which the black queen could travel with check, to her king’s defence. Other moves are simply bad:
A) 18.Qh4? h6 19.Rhd1 Ng6 20.Qh5 a5μ;
B) 18.Qh5? gxf6 19.Rh4 Qe3+ 20.Kb1 h6–+.

Sad for Black, but necessary, otherwise he cannot avoid mate on g7.

In addition to his material advantage, White can add the plus of the weakened enemy king.

Black resigned.

This example reminds us of the importance of knowing the opening well, and thoroughly analysing one’s own games. White had prepared for the game, but Black had done so significantly better.

Beginning a direct attack on the king.

There is already no defence! It turned out that Sergei Zhigalko had had this position on his board at home, and, what is even more important, he remembered its assessment!