The Harry Potter series has been bought by over 400 million people, or 5% of the planet's population. Read by likely twice that number, if not more. Not only read and bought, but worshipped. Of course people will care about what she has to say about things. Basic human psychology. She has an enormous platform and humans tend to assign author virtue (or lack thereof) to their work, and vice versa. She speaks and people will listen, if only due to the inertia of being able to broadcast her message to millions of people within minutes.