While I do agree with
@KiwiBeanie in that JKR was and still is woke except for the tranny question, and that she only opposed the tranny question because of how she feels it erodes her own position as a feminist within the progressive totem, and I would agree that actually the moral guardians were right and Harry Potter
did bring about interest on the occult amongst the youth and eroded christian principles in them (And anybody who disputes this point has never looked closely at what that fandom was like at its prime) that was quite the schitzopost.
For one, I don't think there is a direct relationship between the actual books and how deranged its fanbase became. To this day I cannot tell whether if all fanbases end up being deranged and toxic or if they're all infected by the original sin of the Harry Potter fanbase. Prior to the existence of Harry Potter there were other fanbases that were known to be plagued, like Star Wars, Star Trek and, ahem, Pokemon and Sonic, but I don't think it was anything like the Harry Potter fanbase, which, for the record, had as an innovation and then-unusual a characteristic that it was overwhelmingly female (And female adjacent, that is LGBT).
I'd say that the drift from male to female in the fanbase demographics is much more of a better explanation than the actual content of the franchise, as we're seeing a similar trend of behaviour in other female/LGBT-dense environments like Tumblr, Sherlock, Dr Who, Supernatural, Steven Universe or Miraculous Ladybug. And generally woke is a manner of pander to such a fanbase (See Star Wars and Lucasfilm under Disney).
Speaking of Disney, Disney ditched male demographics at least 15 years ago, with Hannah Montanah, the Jonas Brothers and all those stuff which also had quite unhinged female fans.
I cannot think of a current IP that has a predominantly male fanbase as of current year, perhaps Rick and Morty would be one, or South Park. Dunno, Male fanbases seem to be quite tame and somewhat feminized nowadays. Unhinged males like incels don't seem to attach themselves to media brands like femcels seem to do.
And you might argue that it's because I'm a penis-haver, but I find femcels scarier than incels.
So, in summary, the wicca and astrology shit on Harry Potter fans is less because they were harry potter fans and much more because they were women and women love all that crap. They were loving all that crap when they populated the Buffy fandom, already. This shit is the sort of power fantasy that appeals to women, women dream of solving their problems with magic and men dream of solving their problems with smashing someone's brains.
Simple as.