Why was Naruto never promoted to the Chunin rank?

Naruto, the primary protagonist of the show, is one of the strongest Shinobis in the world. Despite being so powerful, he's still a Genin. Although it would be incorrect to refer to him as the 'Eternal Genin', it is true that he went straight from being a Chunin to being the Kage,

The ninja world in the series has various ranks. Genins are the lowest ranks in the ninja hierarchy, while Kage is the highest rank that a ninja can achieve. In order to be a Kage, ninjas will usually have to proceed through different ranks, but Naruto happens to be an exception. Although he did have the chance to proceed through different ranks during his early days, something happened that stopped him from achieving these different ranks.

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Naruto and his fate of being stuck at Chunin rank

Unlike many other Shinobi, Naruto never really had the time to become a Chunin. Yes, he sat for the exams, but no one really knew how things would have panned out had everything gone smoothly. During the Chunin exams, he went up against Neji Hyuga and successfully defeated him. However, before the exams could conclude, Orochimaru attacked the village. With Orochimaru's attack, the Uzumaki kid lost his first shot at being promoted to Chunin rank.

He did receive another shot at being Chunin but he blew that up. In the Chunin Exams on Fire! OVA, he travels to Sunagakure to take the exams. In the initial rounds of the exam, he gets paired up with his protege, Konohamaru, and the two individuals battle it out.

Both of them looked pretty good on the battlefield. Konohamaru had Naruto locked in his sights and threw everything he had at him. Naruto managed to dodge most of the attacks, but there was one attack that got through to him. Annoyed with the fact that he'd been hit, the Uzumaki kid then activated Sage mode.

However, senjutsu was forbidden in these exams because its usage would be unfair to the other Genin. Since he used Sage mode, the future Hokage was immediately disqualified. It was unlikely for him to break the rules, but later on it was revealed that he was oblivious to this rule because he was unaware of it.

While Temari was reading out the rules, Naruto and Konohamaru were busy arguing amongst themselves like they normally would on any given day. This was the reason he failed to hear the rules while it was being read out. And thus he failed to make it to the Chunin rank the second time as well.

Despite being stuck at that rank, the protagonist was a very powerful Shinobi and had achieved a lot throughout his career. He had successfully mastered many S rank jutsus and had defeated many powerful enemies as well.

After Kaguya Otsutsuki was defeated and the world was safe again, Kakashi was finally made Hokage. As soon as he assumed the position of Hokage, he immediately promoted the Nine-Tails Jinchuriki to the rank of Jounin. But for that, he was required to finish the course. Because of this, in the series, Naruto was never promoted to the Chunin rank.