Only one student became a chunin after the exams were cancelled. How did Shikamaru become a Chunin?
Shikamaru became a chunin after the Invasion of Konoha, despite losing his match and the exam becoming cancelled as a whole. The exam’s coordinators were impressed by the problem-solving, calmness and mercy Shikamaru showed in his Chunin Exams’ match against Temari.
He was the only ninja in his generation to become a chunin during that exam period. Had the exams finished properly, Shikamaru would have been promoted anyways. The exam coordinators felt it was in the best interest of the village to bump him up.
The story behind how Shikamaru became a Chunin
The Invasion of Konoha required all hands on deck. Promoting the brilliant Shikamaru to chunin status provided an extra skilled ninja to join and lead the resistance.
During his fight against Temari, Shikamaru impressed the judges by stalling out his opponent until the nightfall. Shadows provide a more advantageous battleground. He tied a kunai to a cloth in order to act as a balloon that could extend the reach of his Shadow Paralysis Jutsu. Backing Temari into a corner, he used holes in the ground left behind by Naruto to maneuver the shadow underground. He caught Temari from behind.
Chunin Exam participants are evaluated more on the substance of each match than the conclusion. Hypothetically speaking, none of the ninjas could win their matches and all still become elected to chunin. With this information in mind, Shikamaru forfeited his match after catching Temari in his Paralysis Jutsu. He felt as though he proved himself enough to the judges and did not need to continue any further.
In chapter #309, it is specified that his performance exemplified the cool, analytics skills needed to be a good leader. The exam coordinators envisioned Shikamaru as a platoon leader who doesn’t panic or become hotheaded.
Other Thoughts on Shikamaru Becoming A Chunin
Shikamaru became a Chunin when he was 12 years old. His ninja generation was encouraged to take their exams early in order to better prepare for oncoming threats on the village poised by Orochimaru.
Shikamaru’s IQ is over 200 according to his sensei, Asuma. He felt it necessary to trick Shikamaru into taking an IQ test as he found written exams to be a pain. The results showed that Shikamaru was more than brilliant.
Naruto wasn’t made a chunin because the exams were interrupted. He was on pace to be recognized well by the judges after defeating Kiba and Neji in solo battles, but the Invasion of Konoha caused the cancellation of the exams.