visayanbraindoctor: This is an example of playing subpar moves in order to preserve winning chances.After 21. Rc5 Rfd8 question is why did Kramnik not play 22. Na3 followed by Nxc4?
After 22. Na7 Rd2, again why did he not play 23. Rxa5?
In both cases White would have won a clear pawn. However, looking at what may happen with subsequent reasonable moves, the ending probably almost by force goes into 4 pawn vs 3 pawn all in the Kingside, or one in which both Black Rooks become quite active. Along the way black also gets to exchange his Bishop for a White Knight.
One such reasonable variation: 23. Rxa5 Rxb2 24. Nc6 Rb7 25. Rb5 Rxb5 26. Nxb5 Nxa4 27. Rxc4, and although White is a pawn up, Black should have no difficulty in holding the ending.
A 4 pawn vs 3 pawn all in the Kingside ending is a theoretical draw. So are most Rook endings where the defender, even down by a pawn, has active rooks. So Kramnik avoided it and instead began playing for a direct attack on the Black King choosing to retain his two Knights. As crazy at it might look, it was his only practical chance for a win.
His plan is becoming clearer after another subpar move 25. Ncb5, instead of defending his b-pawn with 25. Rb1 which would have allowed sooner or later the simplifying exchange BxNc3.
By 33. Kg2 Nxe2, the game looks dead equal, and it should be except for chances of a mating attack by White, which is what Kramnik probably wanted (since he had decided to retain his two knights as discussed above).
He straightaway plants a Knight on d6 by 34. Nc4 Ba1 35. Nbd6+
Then for the next several moves, White essentially does nothing, just moving his pieces around while avoiding exchanges. The character of the position is such that White can just maintain it almost indefinitely, while waiting for a Black error.
It must be said that Nepomniachtchi defended wonderfully and accurately for all of the game out of an almost lost opening, finding only move defenses. Yet he must have found the knight on his Q3 square a real pain. Imagine having to defend for 50 moves with that knight planted in the middle of your position. And eventually blunder he did, 46.. Be5, allowing a mating attack 47. Nb7 Nc3 48. Nd8, which can only be warded off by sacking a pawn in a compromised position.
Some kibitzers may wonder why this game was not abandoned as a dead draw on move 40. The reason is that humans make mistakes in difficult and annoying endings in which the attacker can maintain the character of the position indefinitely without much risk, while waiting for an error from a non-computer also human opponent. (Among World Champions, Fischer and now Carlsen are particularly good in this kind of strategy.)
Kibitzing
