The end of the Androids Saga created a large paradigm shift for Dragon Ball as a series. Goku died to keep Cell from blowing up the Earth, and then refused to be brought back to life because he believed he was the reason why major threats kept showing up on Earth. This was a big deal at the time, especially since this meant that Dragon Ball's main character would no longer be appearing in the series.
However, Dragon Ball continued with the Buu Saga, this time with plans to have a much older Gohan serve as the main character. Despite all this, Gohan ends up doing very little throughout the Majin Buu Saga, and in the end, Goku is the one who destroys Buu using the Super Spirit Bomb. How did this happen when Gohan was supposed to be the main character of the saga? Did Toriyama write himself into a corner, or was there some outside influence that caused him to go back on his decision?
Gohan As The Main Character
At the beginning of the Buu Saga, Gohan is introduced and presented as the new protagonist for the series. Set seven years after the Androids Saga, Gohan is now a teenager with plans to go to high school in Hercule City. The early parts of the story involve Gohan balancing his school life as he uses his strength to fight crime as the Great Saiyaman. The story at this point has a very different tone compared to previous sagas, but that soon changes once Babidi and Majin Buu enter the picture.
In fact, once Majin Buu makes his appearance, Gohan's presence in the story begins to wane. He is swiftly defeated by Buu, then transported to the Other World by the Supreme Kai and his ally Kibito. This means that Gohan is largely absent for the first half of Buu's rampage around the world. During this time, Goku has temporarily returned from the dead, and the story turns to focus on his actions to stop Buu while Gohan is out of commission. This is an early sign that the idea of having Gohan be the main character has been mostly abandoned.
Gohan's Last Chance
However, Gohan hasn't been made irrelevant yet. The Supreme Kai explains to Gohan that there is a way that he can obtain the power to defeat Majin Buu. At first, they believe that Gohan must pull out the extremely heavy Z-Sword and train with it until he has fully mastered it. However, it turns out the path to true power is hidden in the Elder Kai sealed within the sword. The Elder Kai offers to perform a ritual to unlock Gohan's true potential, and it works. Gohan becomes the strongest he has ever been, so much so that he doesn't even need to become a Super Saiyan anymore.
This strength is demonstrated when he returns to the fight, toying with Super Buu to the point where he is forced to run away. This triumphant moment is short-lived, however, thanks to some cunning on the part of Buu, he is able to catch and absorb Gotenks, which allows him to turn the tables on Gohan. Gohan is beaten to a pulp by the new Buu, and when Goku comes to help, Buu uses a similar trick to absorb Gohan, removing him from the story entirely from that point on.
Why Did This Happen?
Since many people were fairly aware that Gohan was supposed to be the main character of the Buu Saga, there's a lot of fan discourse as to why he's not really treated that way. Some people believed that it was negative fan reaction to the idea of Gohan replacing Goku that convinced author Akira Toriyama to bring Goku back. Others suggested that it was executive meddling on the editor's part, who thought that Goku as a character was more popular and iconic than Gohan. However, no real evidence that this fan backlash had an effect has ever been given, and Toriyama has stated that his editor during the Buu Saga, Fuyuto Takeda, was much more lenient and often let him write as he pleased.
In the end, it turns out that the one who was responsible for pulling Gohan out of the role of main character was Toriyama himself. In an interview, he had stated that while he did plan to have Gohan as the main character, he ultimately felt that he was "not suited" for the part. To Toriyama, Goku was simply better and more interesting as the main character. He has never really explained why he thought Gohan was unsuitable as the main character, but the result was clear; Gohan was reverted back into a supporting character, and Goku took the center spotlight again. Since then, Gohan has had a hard time returning to his former glory, as seen in Dragon Ball Super. Nevertheless, he is still a beloved character, even if he's not the main character, and he's slowly started to rise up in prominence once again.