If I may, comparing fanfiction to original work is apples to oranges.

When writing harry potter, Rowling had to craft a world with characters and rules, make it coherent enough and tread a compelling story through it. She made the legos and then crafted something with them.

This guy came to her crafted world, and moved around a few bits, changed a character here, change a few rules there - but the backbone of the work was made before.

It's just not the same ballpark