It's popular because the relationship between Hinata and Naruto has been a long - developed one in the original series. Fans have been rooting for them for a long time. So, fanfictions about Hinata confessing give fans the satisfaction they didn't get fully in the original work.
There's a fanfic called 'A Confession Long Awaited'. In this one, Hinata's confession is a turning point in their relationship. It's set after a big battle where they both realize how much they mean to each other. The story does a great job of showing Hinata's strength in being able to be so vulnerable. And then there's 'Confessing My Love, Hinata - Style' which is a more light - hearted take on her confession, with some cute and funny moments between the two characters.
Well, in the Naruto universe, Naruto's confession to Hinata would bring a lot of positive changes. Since Naruto has always been the center of attention, his relationship with Hinata would be a big deal. It would probably strengthen the bond between the Uzumaki and Hyuga clans. Also, Hinata has always been a quiet and supportive character, and with Naruto by her side, she could become more confident and play an even bigger role in the village's affairs.
One scenario could be that Naruto is initially shocked but then quickly realizes his own feelings for Hinata. Another might be that Hinata's confession causes a stir in the village as it's a very public event. Or perhaps Naruto is in the middle of a difficult mission and Hinata's confession gives him new motivation to succeed.
Another interesting fanfic could be set in an alternate universe where Hinata is a famous ninja and Naruto is a regular villager. Hinata's confession in this scenario would be different as she has to overcome her status and the social differences to tell Naruto how she feels.
One of the most emotional scenes could be when Naruto finally realizes his true feelings for Hinata. Maybe it's after a dangerous battle and he sees Hinata there, always supporting him, and it just clicks. Another could be when he actually confesses. The look on Hinata's face, probably a mix of shock and overwhelming joy, would be really moving. And the moment when they embrace for the first time after the confession would also be super emotional.
However, in other cases, Naruto could be hesitant. He might have grown so used to their friendship that the idea of a romantic relationship with Sakura is a bit overwhelming. He could take a step back and say something like 'Sakura, this is really unexpected. I need some time to think about this.' This would then lead to a more complex exploration of their relationship in the fanfiction.
In some Naruto fanfictions, Hinata could potentially be portrayed as a 'weapon' in a very metaphorical sense. For example, her Byakugan abilities might be exploited in unique ways that make her seem like a strategic weapon for a side or a cause. But in the canon Naruto story, she is a character with her own agency and not really a weapon.