It could also be due to his old - fashioned values. Edward was born in a different era, and in that era, marriage was seen as a way to claim someone. He might be influenced by those values and think that marrying Bella is the proper thing to do, regardless of her current feelings on the matter.
One possible reason could be his over - protectiveness. Edward might think that marriage would legally bind Bella to him and he could better protect her from the various dangers in their world, such as other vampires. He may believe that as his wife, he could keep a closer eye on her.
Perhaps he is afraid of losing Bella. He might think that if they get married, their bond will be stronger and it will be harder for anything or anyone to come between them. So, in his mind, forcing her into marriage is a way to secure their relationship.
Perhaps she has her own vision of their relationship and doesn't want it to be influenced by the often - strange and varying ideas in fanfiction. Fanfiction can be full of outlandish concepts that she doesn't want to be part of. She wants to preserve the unique and special nature of her relationship with Edward as it is in real life.
One reason could be a shift in the story's setting. If the fanfiction is set in a different time or place, Bella's values and interests might change, leading her to not like Edward. For instance, if it's a modern - day setting with different social norms, she may find Edward's old - fashioned ways off - putting.
One possible reason could be that Sasuke is trying to protect Sakura in his own twisted way. He might think that by making her his wife, he can keep her safe from the dangerous world they live in. Another reason could be related to his family. He might see marriage to Sakura as a way to rebuild his family name or something similar. However, his method of forcing her is completely wrong.
Another reason might be Edward's overprotectiveness. He could have made a decision for Bella without consulting her first, like preventing her from seeing a friend. This kind of controlling behavior could make Bella feel frustrated and end up in tears.
One reason could be that Bella discovers some dark secret about Edward or the vampire world that scares her. For example, she might find out about some vampire politics that could endanger her or her family.
One reason could be for power. Combining their strengths through marriage could make them an even more formidable force. Maybe Sasuke saw it as a strategic move to protect their village or to face some greater threat that they are not aware of yet.
Perhaps there are some who have a darker side to their creativity and don't fully consider the implications of writing about abuse. But this kind of fanfiction should not be encouraged as it goes against the positive nature that most fanfiction communities strive for.
Another reason might be that the fanfiction is set in an alternate universe where their relationship has some fundamental differences. For instance, if the vampire - human dynamic is changed in that particular fanfiction, Bella might avoid Edward because she is afraid of the new and unknown aspects of their relationship.
Some writers might create 'Edward is abusive to Bella' fanfiction to explore the darker side of human nature and relationships. They want to see how the story would unfold if the relationship had a negative turn.
One possible reason could be that some fans want to explore a different dynamic. In the original story, Edward and Bella are in love, but in this fanfiction, perhaps the writer wants to show a more complex relationship where Edward hates Bella. Maybe it's to add more drama or to explore an alternative storyline that goes against the typical romance.