It could be written by fans who are really interested in the concept of 'old crow'. Maybe people who have a passion for the original source (if there is one) that the 'old crow' is related to.
The 'old crow fanfiction' is hard to define precisely without more context. It could be centered around a person, a place, or an object named 'old crow'. Maybe it's a creative exploration of a story that has an 'old crow' as a central element. Fanfiction writers might take the basic idea of 'old crow' and spin it into all sorts of tales, from dramas to comedies, or even mysteries.
Obviously, there is the wise old crow. There might also be other animals like the fox which often appears in such fables as a character that tries to trick the crow.
The main characters are obviously the crow and the old woman.
The Crow comic originated quite some time ago. Its age depends on when you consider its initial release. If we go by the earliest publication, it's been approximately [number of years] old.
Fans of the character Carl usually write Carl fanfiction. They are often people who are really into the story that Carl is from and want to create their own versions of his story.
Fans of Onew write onew fanfiction. They are often people who are really into Onew as an artist, and they use their writing skills to create fictional stories about him.
Obviously, the two main characters in the crow and the old woman short story are the crow and the old woman. The story probably focuses on their interactions, whether it's a friendly encounter, a situation where one helps the other, or some sort of conflict between them. Their characteristics and actions are what drive the plot forward.
There could be many different fans who write it. It might be an amateur writer who just loves Naruto and wanted to explore this unique scenario.
It could be written by amateur writers just starting out in the RWBY fanfic world who see commissions as a way to gain experience and make a bit of money or get some recognition. There might also be more experienced writers who do it for the fun of exploring different ideas within the RWBY universe that they might not have thought of on their own. And sometimes, a group of RWBY fans might collaborate on a commissioned fanfic, each bringing their own strengths to the writing process.
Fans of Robert Pattinson and Kristen Stewart write robsten baby fanfiction. These are often fans who were really into their relationship on - and off - screen and like to imagine different scenarios involving a baby in their relationship.