It’s an iconic scene that exemplifies Naruto’s obsession with saving Sasuke, but why did Naruto pass out in the snow?
Naruto had to pass out in the snow because he realized that Sasuke might not be saved. He’s flooded with thoughts of the others giving up on Sasuke, and he remembers Gaara’s advice that ending Sasuke could be the best way to “save” him.
He has a full-blown, hyperventilating panic attack as the walls are closing in around the possibility of saving Sasuke. The attack on the Five Kage Summit and Sasuke’s classification as an international threat is becoming too hard to justify.
Thoughts make Naruto pass out in the snow
In chapter #476, Naruto learns more information about Sasuke’s location while standing with Kakashi and Sai.
Naruto remembers an accusation from a pair of Cloud Ninja. They say that Sasuke Uchiha of Konoha attacked their village and had a fight against Killer Bee, their teacher. The ninja also informs Naruto that Sasuke was officially working with the Akatsuki.
He also remembers words from Obito, who explained that Itachi’s whole life was about self-sacrifice. Sasuke ending up alone was the cost for Konoha’s peace, and Sasuke completely resents the peace gained from Itachi’s sacrifice. “Hate” being Sasuke’s shinobi-way continues to hurt Naruto.
Sai previously informs Naruto that Sasuke’s former classmates intend to dispose of him themselves. Naruto remembers being told that Sakura, one of Sasuke’s most loyal supporters, is also planning to give up on him as well.
Finally, Naruto remembers the last piece of advice that set him over the edge. Gaara suggests to Naruto that if he “truly [has] resolved to take on the mantle of a shadow, then [he] must do what needs doing as Sasuke’s friend.” Gaara is implying that Naruto may need to dispose of Sasuke if he truly cares about him.
Naruto then puts his hand to his chest and falls to his knees. He crashes down into the snow, hyperventilating while the people around him yell out for Naruto to calm himself.
So that’s the answer. Naruto had to pass out in the snow because he realizes saving Sasuke is likely not possible. He remembers that the others are plotting against Sasuke already, and Gaara advises Naruto that ending Sasuke may be the best way to save him.