i can easily see how you COULD fill 3 movies with everythign that takes place in The Hobbit (the first book I ever read ON PURPOSE - and which led me to a lifelong love of reading, gratefully) - the most he should have tried for is 2- especially if all 3 are not brought out to the theatres in rapid succession.
He wanted to bring out the fullness of the LOTR world. As I recall reading the Hobbit, and it’s been a few years, it was fairly light in its atmosphere, except when Bilbo met Gollum.
As I understand it, Jackson added stuff based on the context for Gandalf organizing an expedition against Smaug drawn from the appendices of LOTR and the chapter The Council of Elrond in the Fellowship of the Ring.
It makes sense to do this with the movie version being released as a prequel since the viewers are presumed to know Jackson’s version of LOTR.
It’s still not clear to me there’s enough there for three movies, but two would be easy.