Wow, that's really hard to say. I've come up with a few ideas
1. Both accounts are actually the same creator. It's possible they created a new one because of negative feedback or just to upload their item multiple times. Either way is definitely against the rules.
2. One of them is the real owner. Guamwork may buy low cost products and reupload them for a higher price, relying on the high quantity of item in their shop to bring in more traffic to the item. Or Faint3d bought the item and then decided to resell it and undercut Guamwork. Again, both would be against the rules.
3. This building model is in the public domain from another site and thus has "no true owner". Both sellers have decided to sell the asset with the original renders independently. I am unsure whether this breaks any rules, but it is unethical.
Doing a simple image search reveals the item is on numerous sites with different authors:
http://www.ddove.com/htmldatanew/20160909/8c39bb1fe5e4e8e1.html
http://www.nipic.com/show/6258247.html
https://3dexport.com/3dmodel-lobby-144-43111.htm
and...
The free model:
http://www.tupian114.com/3d_1677461.html
I think the original model is indeed in the public domain and various authors have since uploaded it.
