In my understanding, they are building a Dropbox/Trello/Deviantart hybrid specific to 3D Models. In my view they are coming up with an MVP that is somehow promising on these lines. How money will flow in [i.e., why power users would pay sketchfab instead of relying on the whole bunch of existing 3D library services] still looks to me a bit of a cryptical point, but they have probably yet to focus on this with some serious customer development.