Why did this cost millions of dollars? An independent studio could do this well-worn story for less than half of what Disney spent on this. Not that the company doesn't have a history of wasting money, of course.
What it is not.
Collage -- ccomputer generated -- cut-out --direct -- mixed media -- object -- pin -- pixilation -- puppets -- silhouette -- still painting -- stills -- traditional
I bet no one knew that there were that many types and styles of animation.
What it is.
It is a whole new type and style of animation blending the best of old traditional animation and new computer generated animation. Which is why it cost so much. And which is why only Disney/Pixar could do it. As they are the only ones with the talent and money to do it. And while most animation is now done in color, it is one of the few that goes back to the old days of doing it in black-and-white.