Why might someone write a fanfiction about Bella Swan not existing?

One possible fanfiction could be about how the other characters in the Twilight universe react to the sudden realization that Bella Swan was never real. They might question their memories and relationships.

Edward Cullen would likely be a main character. His reaction to Bella's situation, whether it's concern for her well - being or struggle with his vampiric instincts around her period blood, could be a major part of the story.

Well, for a start, they could be frustrated with Bella's character development. In the original series, she might not have grown in the ways they expected. So, they write 'bella swan bashing fanfiction' to show how they think she should have been different. Also, it could be a way to explore alternative storylines. If Bella wasn't the main focus or was a more flawed character, how would the story change? It gives them creative freedom to play with the Twilight universe.

Some people write it for the shock value. Changing a major character's fate like Bella's death can create a whole new narrative that grabs readers' attention.

Well, it could be that some elements of her character seem too contrived or idealized in a way that doesn't feel true to the source material. Maybe her actions and reactions are not in line with what a real fan would expect from a legitimate character in that fictional world.

It could also be an exploration of character development in extreme situations. What would Edward become if he did such a thing? How would the other characters change? Writers might use this extreme scenario to show how the characters would react and grow, or in this case, maybe degenerate in a different way compared to the original story.

Edward would definitely interact differently. If Bella goes back in time and changes her initial approach, Edward might be more or less intrigued by her. For example, if she's more confident, he might be even more drawn to her than in the original story.

Maybe she had some deep-seated fears or insecurities that made her do it.

Maybe she had some deep fears or insecurities that made her do it. Trying to hide her true self for protection or to fit in.

Some people might write it to explore a darker, more alternative take on the characters. They could be interested in seeing how the story would change if Dumbledore had a more sinister side. It's a way to break the established perception of the characters.