In fact, one of the weirdest phenomenons in the whole story of Potterville has been the backlash against religious fundamentalists that has been almost as, well, radical as the original fundamentalist reaction to the books. While the usual suspects came out at the beginning and labeled Harry Potter as the textbook of Satan, a stalwart bunch of Christian fans of the series fired back. Not only was it not of the Devil, but soon it became a reflection of the Eternal Truth, where every page and paragraph oozed Christian Gospel. More than that, some (oddly enough in the blogosphere) went so far as to suggest only idiots or those whose spiritual being was somehow deficient could ever miss the fact that the Potter Saga deserved to be placed somewhere between Matthew and John.
Perhaps it's just me, and maybe because I haven't read all seven of the books, but from what folks have said, what Rowling has said, and the general response to the books has suggested, I must be dumb or spiritually inept. For I don't see a series of books written by a sage scholar of the deepest insights trying to promote the orthodox Christian faith. I see a woman who, as my oldest boy has said in so many words, is a decent author but a phenomenally brilliant and capable business woman. One of her greatest gifts (powers should we say) is the ability to speak to a diverse range of fans and convince them that she is writing for them. She's not dead. She didn't pass from this world a hundred years ago, where debates about her intentions and themes are the stuff of academic theory. She's alive in the Internet age. And yet she still maintains groups of fans who insist she speaks to them, that her books are a celebration of post-modern new age occultism, or a validation of European secular liberal values, or a tome laying down the framework of the traditional Christian faith for a new generation. All insist they are right because she is more brilliant than a Washington politician when it comes to saying just enough, but never more.
I have my own opinions, of course. And it's not because I have anything against the books. I think they are cute; the early ones especially are nice children's books. Prisoner is my favorite, and I think the best of the series. The later ones perhaps had her overreaching her writing abilities. But overall they appear rather inoffensive, and have a few nice lessons like self sacrifice and loyalty. There are also a few lessons not so nice, particularly the idea that authority is always to be resisted and when you're the good guy, there's no rules, just right.
As for why the change in style and, to be blunt, quality? Some of the confusion could be, like my oldest (and our resident expert on the Potter books) said, her books appear to have two distinct phases. The early ones, when she was just beginning, appear to be part of an overall storyline that she was developing that find its crescendo in the third book, Prisoner of Azkaban. Somewhere between book four (Goblet of Fire) and book five (Order of the Phoenix), things change. Many fans, and critics, argue the books loose a little there, are not as well written, and generally try to go too many directions at once.
Why? My guess is, and at least one theory I read suggests, she realized a major change had to happen. The first books give every impression that Harry was the tragic hero, doomed to die or suffer some Frodo-like fate to save the world. But as HP became the first fruits of the new era of international market access, a development that has opened the door to unprecedented success for such stellar works as the Twilight series and Avatar, it became clear a major change had to take place. Harry could never, ever die. No way. There is a multi-billion dollar international Potter Corp. to consider. Get rid of Harry, and it's all over. My other boys attest that while still somewhat popular, Harry Potter has been eclipsed by other works over the last year or so. Harry had to live, to go on, for multi-billion dollar corporations must be maintained.
Yet even a cursory reading of the early books suggests Harry was being set up as the great, tragic hero, something Rowling herself hinted at many times in early interviews. So when it became clear that killing off Harry would have been like killing off Mickey Mouse, changes had to happen. Other characters had to be elevated so that when the time came, and the promised final book was released, the 'tragedy' would still happen - in that key figures who had become major players could still be offed in order to fulfill the requisite 'this is an unusually tragic tale for a kid's book' - while keeping the principles alive for that magical day when Rowling could forget her lifelong promise (that there would only and ever be seven Potter books), and begin laying the groundwork for more
At least that's my guess. All of this is to say be careful how one plows into the modern artificial world of popular culture. If corporate heads and politicians are merely corporate heads and politicians, that may sometimes apply even to those whose products we admire. Sure, for those who looked at Harry Potter and said it's of the Devil, unless you can prove it beyond 'it has wizards doesn't it?', consider backing off and not making the Christian faith look stupid. But for those who attempted to elevate it to the level of St. Rowling and the Holy Potter, consider that she simply might be a decent author who is a brilliant business woman, promoting a mixture of classical themes that Christianity certainly can claim, but also infusing it with plenty of European post-modern notions of individualism, anti-authority, and affirmation of anyone for any reason who does anything as long as they are not a baddie. And when the magic dust has finally settled, its main purpose may have been focused on maintaining yet one more multi-billion dollar corporation above all things.