Perhaps the story is set in a chaotic or dystopian world where memories are easily lost or manipulated. Or, it could be a plot device to make the character feel isolated and drive the story forward.
Well, it might be that the story has some sort of mind-altering element that wipes people's memory of you. Or maybe it's a test for your character to overcome this lack of recognition and make a mark.
It could be that the world in the light novel is too big and chaotic, and people have their own concerns and distractions. So, it's easy for them to forget about you. Also, if your character doesn't have standout qualities or actions, it's harder to be remembered.
Maybe because people are too busy with their daily lives. They have to work, study, and take care of various chores. There's little time left for reading stories.
It could be due to the fact that there are so many different interpretations of Hermione in fanfiction. Some might not like the way she is portrayed as being too perfect or too flawed in certain stories. Also, if the fanfiction doesn't add anything new or interesting to the existing Hermione character arc, it may not attract readers.
Perhaps the themes or characters weren't engaging enough. Maybe it was released at a time when there were many other popular manga stealing the spotlight. Or it might not have been available on popular platforms where people tend to discover new manga.
Perhaps it was overshadowed by other more popular novels at the time. Or, its themes and storylines were too niche to capture a broad audience's attention and memory.
Well, there are so many fanfics out there that it's easy for some to get lost in the shuffle. Also, with new shows and stories constantly coming out, people might move on from Naruto fanfics.