It could be that he had a severe mental illness that drove him to such a desperate act. Or perhaps he experienced a sudden, traumatic event that shattered his will to live.
One reason in fanfiction could be the pressure he faced. Draco was always under the pressure to uphold his family's reputation. He might have felt trapped in a role that he didn't fully embrace. And as he grew older, he saw the hollowness of it all. He may have compared himself to others who seemed to have more freedom to be true to themselves, and this led to self - loathing. For example, when he saw Harry and his friends being so carefree in their friendships and beliefs, while he was constantly constrained by his family's expectations.
Perhaps in the fanfiction, Naruto discovers some dark secrets about his past, like his family's involvement in something he considers immoral. This new knowledge could make him question his own identity and lead to self - hatred. He might feel that he's a product of something bad and that he can't escape this 'taint' no matter how hard he tries.
Another reason could be related to his origin. In fanfic, if his Uzumaki heritage is explored in a way that makes him feel like a burden or an outcast more than in the original series. Maybe there are secrets about his family that make him question his own worth. For instance, if there are made - up prophecies or family curses in the fanfic that make him think he's doomed to bring misfortune, he could end up hating himself.
Well, it could be due to a complex web of motivations and storylines. Maybe she was manipulated or had a misunderstanding that led to such a drastic action.