When Mr. Satan first appeared in Dragon Ball Z, a lot of fans didn't like him. At the Cell Games, he trash-talked the Z Fighters, dismissed their feats as magic tricks, and took all the credit for defeating Cell. He was certainly not the hero he made himself out to be.
However, not everything Mr. Satan did in the narrative was necessarily bad. In fact, there were ways that he was a useful and even necessary presence. He arguably did even more than some of the Z Fighters to save the world. In this regard, Mr. Satan really is a hero, just not the kind that everyone thinks he is.
Many immediately write off Mr. Satan as useless in this arc because he did nothing as a fighter. He went up against Cell and was swiftly removed from the ring. After this, he spent much of the rest of the Cell Games staring at the Z Fighters' unbelievable fights mouth agape. For what a joke of a character he was, nobody could be faulted for remembering him as irrelevant.
While Mr. Satan can't fight on the Z Fighters' level, there are ways that he managed to help out. One of his biggest assists came in the form of Android 16's disembodied head. Without a body, the Android needed somebody to carry him over to Gohan so that he could give him some sage advice. He tasked Mr. Satan with this important duty, which the World Champion couldn't refuse. He braved no man's land to get the Android head to Gohan before the Cell Juniors could kill his friends and family. In a sense, Mr. Satan could be considered indirectly responsible for Gohan's ascension.
Another thing Mr. Satan helped out with is assuaging the fears of the masses. While the Cell Games were meant to be seen by the world, hardly anybody knew who their saviors were supposed to be, and that's just how the Z Fighters wanted it. This was why the Royal Army attempted a preemptive strike on Cell only to be wiped out. Even after that happened, Mr. Satan was there to ensure everyone that humanity would not be destroyed by Cell. Without him, the world might have been thrown into even more of a panicked frenzy than it already was.
Furthermore, fans hated him for it, but taking credit for the Z Fighters' victory was also important. As much as the Z Fighters might have liked to be properly credited, they also understood that they would have been relentlessly hounded by the media. They kept their identities a secret so that they and their loved ones could maintain their privacy.
This is where Mr. Satan being a glory hog comes in handy. Unlike the Z Fighters, he absolutely eats up media attention. He enjoys the cheers and praise of his fans around the world, even if it's undeserved. Thus, the process of the Z Fighters saving the Earth and Mr. Satan getting all the credit and media attention has become the norm for Dragon Ball.
While Mr. Satan initially comes off as a useless jerk, he's proven to be an invaluable part of the plot. Besides the assist he provided Android 16, he essentially acts as the public face for the Z Fighters. From his podium, he is able to instill trust and a sense of security among the masses. This is in stark contrast to the Z Fighters, who show little to no interest in the spotlight. Mr. Satan's sense of stage presence and his ability to capture the hearts of people are what make him a real hero.
