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You know how in the Chunning Exams arc Naruto and Sakura deepened their existing bonds with certain people and even create new bonds with new characters? While Sasuke slowly but violently drifted away from their circle of influence, going towards what Orochimaru offered?
The Chunning Exams allowed Naruto to confront Neji and his ideals, allowed him to start or further the depth of his bond with Hinata, to create the connection Gaara and him shared, something that would last for life. We have those moments with Shikamaru and Rock Lee, stuff that cemented his place on Konoha, showed us Naruto acting not in a team of three but in a wider range. The first step to become Hokage, not doubt.
It also gave us important moments for Sakura. We got her relationship with Rock Lee, something that started as a joke and turned into to mutual respect and appreciation. We got a development and explanation of her rivalry and friendship with Ino, we got to see Team Asuma reacting to her fight against the Sound and the jounins reacting to her fight with Ino. We got to see moments that meant a lot for her in Team 7 and showed us how much she meant for Naruto, Sasuke and Kakashi.
But Sasuke? Every possible rivalry or connection was given to Naruro or pushed aside. Sasuke was one of the first to challenge Rock Lee and Gaara, but the Rock Lee fight was taken by Gaara and the Gaara fight was taken by Naruto, later on the invasion. Since he was away from the other fights due the cursed mark or his training with Kakashi, he didn't get to see Neji or anyone else fighting. We never saw the Sound ninjas again, which left us with Sasuke only having bonding moments with his team— even those were negative if you think about how Sasuke must have seen most of them as failures. Exactly like Orochimaru had told him, he was not strong enough to either protect his team or defeat the enemy, but Naruto was.
Sakura and Naruto were really the only two who could have kept Sasuke from leaving or brought him back, because to Sasuke's eyes Kakashi had failed to offer Sasuke the power he craves for.
Sasuke didn't get the chance to develop any kind of relationship with anyone else, foreigner or from the Konoha 12. So inevitably when his relationship with Naruto decayed (for many reason like Itachi chasing Naruto and not Sasuke, or Naruto being the one who saved Sakura and defeated Gaara), and when he started seing Sakura as a weak point (in the sense that he realized that listening to her wouldn't give him any type of physical strength), it was obvious they'd fail to give Sasuke a reason to stay with them.