I guess such stories come from a warped mindset. They have no positive value and just try to sensationalize and be provocative. They don't contribute anything meaningful to literature or understanding of relationships.
Sometimes, it might be because of external influences, such as bad company or financial stress. Or it could be an internal struggle with one's own desires and values. Also, a traumatic event could potentially lead to such a transformation.
I recommend "She and the Vampire Count." The male protagonist, William III, used the "Embrace" method to turn the female protagonist into a vampire. What kind of magical journey will she have waiting for her next? I hope you like this fairy's recommendation. Muah ~😗
Some wives might initially feel shock and disbelief. They could choose to go through therapy, either alone or with their husbands, to try and understand what is happening. For example, they might seek marriage counseling to see if there are ways to salvage the relationship, even if it means changing the nature of it.
The reasons can be complex. Maybe they face betrayal and seek revenge in a wrong way. Or they might be lured by false promises of a better life. It could also be a result of a sudden change in circumstances that they can't cope with properly.