The Lord of the Rings will go down in history as one of the greatest book to film adaptions ever undertaken. When J.R.R. Tolkien released The Lord of the Rings in 1954, it soon became a cultural phenomenon. He flipped the fantasy genre on its head. People began to realise that fairy tales weren't merely for getting children to sleep, they could be epic stories that struggled with the dichotomy of good and evil, imparting moral lessons, as well as being a source of entertainment.
Adapting this story for the big screen was a huge undertaking, but through care, dedication and respect for the source material, Peter Jackson and his team pulled it off. After the success of the movies it was only a matter of time before the Hobbit would get a similar treatment.
The book of the Hobbit is a far less complex story than the Lord of the Rings, and therefore should have been far easier to adapt to the big screen. So when it was announced we'd get another cinematic trip to Middle-earth fans had little to no reservations.
So what went wrong? The short answer: EVERYTHING.
10. Not Making It A Prequel
The Lord of the Rings was released some 20 years after The Hobbit, and although it expanded the world of Middle-earth, narratively and thematically speaking, it wasn't a sequel. The Hobbit was an adventure story for children, about Bilbo's quest to reclaim a mound of lost treasure. The planned sequel become something else entirely - a grand and epic tale for adults, about the struggle between good and evil. Tolkien even stated that The Lord of the Rings was not the true sequel to the Hobbit, but to the Silmarillion.
Although Bilbo's Ring later turned out to be the One, this is irrelevant in the Hobbit, the same is true of the Necromancer being Sauron. Tolkien just used these plot points to tie his two stories together, but the central conflict in the Hobbit has nothing to do the central conflict in The Lord of the Rings. In his expanded writings, Tolkien did lay out that Gandalf was motivated to help the dwarves slay Smaug - because he was afraid Sauron would recruit him to his cause - but again this was a supplementary piece of information, rather than a key plot point in the Hobbit story.
Instead of Peter Jackson treating The Hobbit like the standalone story it is, he shoehorned in all these aspect, to make it seem like Sauron's bid for world domination was intrinsically linked to Bilbo's story - and it just wasn't.