Forrest Gump, from beginning to end, lived a life that was self-absorbed. This isn't to say he was selfish; it's because he lived alone in his own world and never needed to (and was lucky enough not to) change himself according to others' standards. Even his mother only told him "Life is like a box of chocolates, you never know what you're gonna get"! Of course, as we can see, due to that kind of stubborn simplicity, his world was more colorful than many normal people's.
He thought American football was simple ("Just Run") and thus made the All-Star team and was summoned by the President, he pulled down his pants in front of the President to show his bullet-riddled butt, he suddenly had the urge to run and without stopping ran all the way from one ocean shore to another, Jenny's feelings were somewhat trivial but only Forrest was there at her grave... Forrest lived in his own world, just like Raymond in "Rain Man" who had autism.
Xu Sanduo was different. His growth process in the military camp was actually a process of getting closer to others (let's temporarily call them "normal people"), or to put it more harshly, a process of compromise (many people may have forgotten, Xu Sanduo initially didn't want to join the army). Everyone thought he would be a burden and drag everyone down, but he became an elite soldier, an outstanding member of the military camp.
What kind of soldier counts as an elite soldier? Clearly, this standard wasn't Xu Sanduo's. So, he had no choice but to grit his teeth and strive with his innate foolishness, stubbornness, and tenacity. Moreover, this striving wasn't spontaneous on Xu Sanduo's part. His father's slaps, Shi Jin's sympathy, Wu Liuyi's hostility, Gao Cheng's lack of... all became the motivation for Xu Sanduo to persist. Don't forget, he often said in front of others "I don't dare, I'm scared".
Therefore, it might be better to say that everyone made Xu Sanduo into the person they hoped he would become, rather than saying that his unique innocence and kindness turned him into a star of the military camp.