.OBJ sucks at keeping smoothing groups as they should be and removes bones
It doesn't seem like the problem is in .obj to me, exporting and then importing .obj into 3ds max works like a charm, while exporting with a blender preset to blender, as seen above, breaks smoothing groups. I tried out tons of formats, .3ds, .fbx, .dae, .stl - none of them work properly, either the model has no materials, or no smoothing groups.
I can ofcource import into blender and then re-do smoothing groups, but the issue is in the fact that I never used Blender and don't have an idea on how to apply smoothing groups, and plus the model has 1266 faces so far - fixing the model will take a while.