This isn't the whole story, but its end - or rather, the end of the part that brought Hikaru Nakamura across the threshold, enabling him to qualify for the Candidates for the second time in his career. (The first time was in 2016.) Four players were still in the running for a Candidates slot going into the last game of pool play (the winners of the four pools go on to the knockout stage): Maxime Vachier-Lagrave, Leinier Dominguez, Levon Aronian, and Nakamura. MVL was in Pool C, Dominguez in Pool B, and the two Americans, Nakamura and Aronian, were in Pool A.
MVL needed to defeat Sam Shankland to keep his hopes alive, but despite his excellent prep (paying careful attention to obscure email games!) Shankland defended like a boss and drew the game.
Dominguez would have retained a chance with a win or even a draw against Vincent Keymer, but a big tactical error in a worse position led to his getting knocked out of the hunt.
That left Nakamura and Aronian, who were tied for the lead in group A. Nakamura and Aronian had Black against Esipenko and Oparin, respectively, and they both got into trouble as well. Aronian in particular had a terrible game, losing speedily and brutally to Oparin. Oparin now led the group with 3.5 points, and with Esipenko on the attack might have won it. Esipenko missed a subtle chance to win, but still retained equality almost to the end of the game; had he done so, Oparin and Nakamura would have contested a playoff. Instead, Esipenko erred in probable time trouble, and Nakamura pulled out the win - of the game, the Pool, and of a Candidates spot, along with Jan-Krzysztof Duda.
Here are those four critical games, with my comments.