Not a Potter/Rowling follower, I can’t see her point...except that it will get the anti-Potter/Christians to despise her, to dig in deeper. I agree it was a huge marketing fiasco.
Now that she has sold all that she can really sell and ended the series she wants to “maintain control”.
By killing the series, she keeps control.
It will be interesting to see how whoever takes up the pen treats Hermine. Hermine is Rowling’s admitted surrogate in the books.