For that you have to understand the system of skeleton based animations, don't worry, it's not very complex.
For every character there is an animationset (a lot of animations and one skeleton). The animations tell the skeleton where which bone has to be moved. The skeleton looks for example like that (without discriptions):

Every vertex point of a model has to be linked to one of these bones of the skeleton if it should be affected from animations. So thats why every vertex point of a 3d model that is not a building is linked to a skeleton bone. If you try to import a 3d model you first have to import the skeleton and then the model. Otherwise the vertex points think the bone is at (0,0,0). Thats why all your vertex points are at (0,0,0).
I hope I could help.