It’s not really baffling.
She is a very powerful, very successful woman who is outspoken in her defence of women’s rights.
Not only that but she puts her considerable financial resources where her mouth is.
JK Rowling is far too rich to damage financially.
They can’t complain to her boss and she’s too successful to put pressure on her publishers or other business partners.
She’s so rich and powerful that threats of malicious prosecutions or reporting her to the police for her social media posts are ineffective. Not many people can wield legal representation with quite such an insouciant approach to the cost.
Being mean about her, and getting people she knows or is professionally associated with to be mean about her is really all they can do to hurt her.
All the usual tactics are ineffective.
And even their current tactics seem to be like water off a ducks back. However she feels privately she’s not giving any quarter publicly.
Not many people, let alone women, are in such an unassailable position. And even fewer have either her courage or wonderful way with words.