In the manga, the class representative wasn't a character, instead, the girl stealing the anime DVD was the chairperson from the end of the episode and was a test essentially. The anime just tied those events very little reason. The more annoying part is the reason Kagami was fired. In the manga, it was because he was being replaced by a proper substitute teacher, who disrespects Kagami since he doesn't follow the rules of society. Then, the sub teacher is a dick and makes a short speech saying the rules of society are important. Kagami then basically reverses the situation which leads to the same ending with them cheering. This makes sense and tries to show that simply following the rules of society won't promise you anything and remember to follow your dreams. The anime on the other, has Kagami fired because he's too selfish to defend himself, not because he has little in the say in the matter (in addition to being selfish) like the manga. They don't try to play this way to their advantage to try to make it a reversal of expectations and basically do the same thing as the manga. This doesn't work since there's no proper antagonist and the conflict is hardly related to the point of Kagami's speech. It doesn't make Kagami cool, it just makes him good at defying the rules in addition to just being selfish earlier