Sort:  

They were compensated (assuming they were paid for the original agreement) and my comment you are replying to expands on my opinion on that. In short, the initial purchase is the compensation. I have no clue in such situations if the original artist should be cited or not. I would assume if the artist wanted their name cited they would include that it needed to be so in the the license agreement/contract. If it isn't there I will have to side with the possibility that citing them is optional or potentially not even wanted by the seller of said asset.

Even with Creative Commons licenses, you are required to give attribution to the original creator.

The licenses they agreed to when they purchased the assets state that they cannot do what they did. They are already investigating remediations.

Just another stain on their already frail reputation..