In a fanfiction, Naruto could also give up his dream due to the discovery of a dark secret about the Hokage position. Maybe he finds out that the Hokage has to make sacrifices that go against his moral code. This realization could make him step back from his long - held dream of becoming the Hokage.
Another reason might be the loss of important people. If someone like Iruka or Kakashi, who were his pillars of support, were to die in a way that made Naruto feel it was all in vain, he could give up. He might think that without them, his dream doesn't matter anymore.
One reason could be the constant setbacks he faces. He might feel that no matter how hard he tries, he can't achieve his goal. For example, if he fails too many times in battles against strong opponents, he could lose hope. Another reason might be the loss of important people in his life. If someone like Iruka or Kakashi, who have been his pillars of support, were to die, it could shatter his dreams as they are so closely tied to his will to succeed for their sake.
Perhaps the death of a key person in his life could lead to him abandoning his dream. If someone like Iruka or Kakashi, who were important mentors to him, died in a way that made Naruto question the purpose of his dream. He might think that without their support and guidance, his dream was no longer worth pursuing.
In some fanfiction, Naruto could give up on Sasuke if he falls in love and his new relationship makes him see things differently. His new partner might convince him that Sasuke is a lost cause or that he should focus on their own future instead. Also, if Naruto suffers a major setback in his own life, like losing a dear friend in a fight related to Sasuke, he could lose the will to keep chasing Sasuke. This would be a very emotional and complex turn of events in the fanfiction world.
One possible reason could be that Naruto realizes Sasuke is too far gone in his quest for revenge. Naruto might see that no matter how much he tries, Sasuke won't change his ways, so he gives up. For example, if Sasuke keeps attacking innocent people in his pursuit of power to defeat Itachi's enemies, Naruto might finally lose hope.
One possible reason could be that he has seen too much destruction and chaos caused by magic. He might feel that it brings more harm than good, so he decides to give it up.
It could also be due to a misunderstanding. Some false information might have spread in the fanfic's world, making Naruto believe that everyone has turned their backs on him. Like, some bad guys framed his friends, and Naruto, being unable to see through the lies at first, gives up on everyone in despair.
One possible reason could be a series of misunderstandings. Maybe his family made decisions that he felt were against his principles or dreams, and after repeated attempts to reconcile the differences, he just lost hope. For example, if his family was against his ninja way, which is such a core part of his identity.
Another factor could be the nature of his ninja life. It's full of uncertainties and risks. He may worry that if he falls in love, his loved one could become a target for his enemies. Naruto has made many enemies over the years, and he wouldn't want to put someone he loves in danger, so he decides to give up on love.
One possible reason could be that he experiences a great loss, like the death of a dear friend. This might shatter his confidence and make him lose his passion for being a ninja.
Itachi could have realized Naruto's potential and determination. He knows Naruto is different from other ninjas and has a unique ability to change people's hearts. By giving Naruto his Sharingan, Itachi might be ensuring that Naruto has the power to carry out some important mission or to protect the people Itachi cares about.