This is insane. It's a lazy copy-paste work from that seller.

You are correct in many things you wrote about. POD marketplaces are flooded with copyrighted works that are not legal to sell. But these people are making money from it. Even 2 or 3 months can give you an interesting income. This is a reason why they do it. Quick money.

For many regular sellers, having an Etsy shop is a business. With all the aspects involved... brand building, community building, promoting... it is about a long-term game.