Well, it makes him more cynical. Normally, Naruto is a very positive and hopeful character. But in this fanfic, giving up on everyone would turn him into someone who doubts the goodness of people. He would become more withdrawn and less likely to reach out to others.
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.
The story could take a dark turn. Without his heart, Naruto might become a soulless being, and his friends would be devastated. They might try to find a way to get his heart back. Maybe they search for a powerful sage or some ancient magic that could reverse what has been done.
If Naruto gives up on his friends in a fanfic, it would be a huge departure from his character. Naruto is known for his unwavering loyalty. His friends are his strength. Without them, he might become a much darker and more isolated character. He could lose his drive to become Hokage as his friends were a big part of that motivation. Also, the village that values friendship and bonds might see him in a different light, and he could face a lot of ostracism.
One reason could be exhaustion. Naruto has been through a lot in the original story. In a fanfic, if he is continuously put through more and more difficult situations without proper breaks, he might just give up out of sheer tiredness.
One possible reason could be to protect his friends. He might think that by sacrificing his heart, some great danger or enemy would be vanquished, thus ensuring the safety of those he cares about. For example, if there was a powerful curse that could only be broken by his heart's sacrifice.
His character development could take a more self - reflective turn. Giving up on love might force Naruto to look deeper into himself. He might question his own values and what he really wants out of life. This could lead to him becoming more mature in his decision - making, not just in terms of the village's affairs but also in how he relates to others on a non - romantic level. He could become more empathetic towards those who also sacrifice personal happiness for a greater cause.
One reason could be the sacrifices he has to make for the village. Naruto is so dedicated to protecting Konoha that he might feel he doesn't have time for love. His responsibilities as Hokage are immense, and he has to constantly be on guard against threats. Another reason could be past traumas. He has lost many people he cared about, like Jiraiya. This could make him afraid of getting close to someone again and losing them, so he gives up on love.
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.