The thing with boycotts is that it's such an online thing. You can proclaim a product or an author the product funds to be problematic morally, call to boycott it to support some cause, and most people are indeed going to join the boycott then post about it on social media, do the moral song-and-dance to join the cause.
In reality, the vast majority of those people aren't invested in the product or the world and wouldn't have bought anything from it, boycott or not. It's much harder to say no to things when you're actually invested into them, meaning boycotts aren't likely to influence those people. With that in mind, you now have a bunch of free advertisement for the product in a sense that it won't leave the public consciousness, a bunch of people not interested in the product doing their "activism" and a bunch of fans of the product fighting the boycotters (as seen with Hogwarts Legacy for instance).
I haven't read or watched or played a single product from JK Rowling's catalogue, but I've seen this happen time and time again with other media or companies such as the infamous Blizzard.