Yamcha saved the world by not doing anything with Bulma.
The Dragon Ball franchise has had among its ranks several of the strongest characters of the manga and anime, being so the power of Goku and Vegeta today is immeasurable despite the fact that Frieza currently holds the position of the strongest warrior in Universe 7.
In this way, it must be said that this has had consequences with some of the classic Dragon Ball characters, since, for example, Yamcha has stopped training and he has decided to abandon the battles, even though he only returns to practically be humiliated. In fact, putting Yamcha further down, it turns out that his most famous defeat is a copy of another Goku suffered.
Yamucha’s adultery was what made Trunks’ birth possible.
In this way, it can be seen as Yamcha has been relegated to a secondary rolethis being something that has already been happening since Dragon Ball Z despite the fact that in its day defeated Goku in his Ozaru form when I was a child. However, remembering his time in Z, it must be said that Yamcha was key at a time that forever changed the history of Dragon Ball, this being something that, ironically, dishonors him even more.
This is because, despite being Bulma’s partner, he did not stop cheating on her with other girls, which ended up pissing off the most famous female character in the saga and caused her to finish off Vegeta. And it was like that Trunks was bornbeing possible in this way that Bulma could dedicate resources in the future to create the time machine and send her son to the past, thus giving Goku the necessary medicine to save his life.
Thus, Yamucha saved the world by not marrying Bulma., this being what marked the future of the events of the Cell saga. Undoubtedly a fact that, in a certain sense, can be unpleasant despite the fact that he cheated on Bulma, but it seems that his humiliations are justified at the same time that time has given him a new girlfriend outside of the canon.