Others take the Chuunin Exams in order to get promoted.
Uchiha Che took the Chunin Exams more to improve his strength, attract Danzo's attention, and tell the world that an Uchiha boy is rising!
As a time traveler, Che carefully hid for ten years.
Watching Naruto, Sasuke, and Sakura form Team 7, and watching Kakashi take them on a mission to the Land of Waves, he knew that the timeline had reached the place he was most familiar with.
Hanging sheep's heads and buying dog meat