Wait, was it a draw? Now I'm very confused. #MTGChamp— Luis Scott-Vargas (@lsv) September 2, 2016
It wasn't just you, Luis. The casters and everyone else were confused as well.
First, let's set the facts straight.
In the fifth and final additional turn, Tiu was at 2 life and had eight untapped lands and a Tireless Tracker on the battlefield. He had plenty of cards in hand, including an Elder Deep-Fiend. Rubin, on the other side of the table, had an 8/8 Octopus token, three Lumbering Falls, and thirteen other lands on the battlefield.
Rubin animated one Lumbering Falls, which Tiu allowed to resolve. Rubin then animated another Lumbering Falls. If Tiu had responded by hardcasting Elder Deep-Fiend at that point, tapping the 8/8 and the to-be-animated Lumbering Falls, then Rubin could maximally present two attackers while Tiu could block both.
Tiu, however, let that Lumbering Falls activation resolve, and now there were suddenly two hexproof creatures on Rubin's side, giving him a window to win if he had just declared attackers. After all, if Tiu would have flashed in Elder Deep-Fiend at that point, tapping the 8/8, then Rubin could respond by animating a third Lumbering Falls and still present a lethal attack.
As Tiu was processing that and going through his options at the beginning of combat step, Rubin said "it's a draw," extended his hand, and signed the result slip.
Steve Rubin's Perspective
"I knew he had Deep-Fiend, so I knew it was going to be a draw," Steve Rubin told me today, indicating that he had already thought through the entire turn, figured out the optimal play not only for himself but also for Tiu at every decision point, and concluded that a draw was the solution to the puzzle. This is typical for top-level players: they think five steps ahead, figuring out their opponent's moves along the way.
"But in my head, I wasn't actually thinking what he needed to do to mess up. And when he did it, I didn't realize it. I was just so locked up in the mindset that it was a draw."
Oliver Tiu's perspective
Oliver Tiu confirmed that he did not play optimally that turn. "I understood the interaction between the Lumbering Falls and the Elder Deep-Fiend, but I just completely missed the fact that if I let him resolve the second Lumbering Falls, then he doesn't have to activate the third one, and I just lose from that point," Tiu told me. "I felt lucky when Steve said it was a draw. I was fortunate that he missed it."
Remember That the Competition is Intense
Small mistakes like these happen all the time, even to the best players at the highest level. It just goes to show how complicated this game is. But to understand the mindsets of these players, you need to grasp the difficulty and intensity of the competition.
These players had been up all day playing close matches against the best players in the world for 10 hours straight. Tiu and Rubin's final game in particular—go watch it again—had already been a 40-minute marathon with two decks that required planning several turns ahead to set up Part the Waterveil and Elder Deep-Fiend wins while guarding themselves against an opposing Emrakul, the Promised End. It was not easy. And from my own experience, I can say that when you go that deep into the rabbit hole, you sometimes miss the most basic things.
As Oliver Tiu can attest, there is a real risk in delving too deep into possibilities—you can't overlook reality.
As Tiu said, "I was playing around way too much the entire game, and I think I actually should have won a while ago. Normally, I make mistakes because I don't think enough, but this time I made mistakes because I overthought the entire game."
"I'm sure it wouldn't have happened if it wasn't the last round of the tournament here at the World Championship," Tiu continued. "We were both very fatigued, playing against the best in the world."
Rubin also mentioned how he felt upset and how that may have affected his mentality. Earlier that game, when Tiu cast Emrakul, the Promised End at 5 life and Rubin's hand was Crush of Tentacles and Part the Waterveil, Rubin felt that no matter what, he was going to win. "He can make me Crush, but then I win with Part. And he can cast Part, but then I get two extra turns so I can make an 8/8 and attack." But then Rubin's draw step revealed Summary Dismissal, which Tiu could use to exile Part the Waterveil, and the envisioned victory did not occur. You can see the crushing realization dawn on Rubin's face here.
Dealing with Mistakes
"The most important thing is to relax and enjoy yourself while playing," Rubin humbly said when I asked how he deals with these things.
Steve Rubin and his Elder Deep-Fiend agree: mistakes are okay if you learn from them.
This mindset extended to the World Championship as well: "It's an intense tournament, but at the same time it's also very friendly. It's a bit more relaxed than you would imagine, and everyone has a lot of respect for each other." This is also why the World Championship competitors weren't berating each other for their mishaps—they all realize that Magic is too deep and complicated to play flawlessly every game, and instead they focus on actively trying to improve on any mistakes.
"It's a silly rule, but I give myself one mistake per day. Otherwise, if I get upset or tilted, then I play worse. So I know I'm going to make a mistake and won't feel bad about it. That rule has helped me a lot."