I don’t think they should have done that, but that’s not my call. It might not be very pleasant to get a bunch of asks accusing you of copying someone else’s work. In my ask I requested that they credit the artist and work they were referencing when posting a copy of someone’s work. That’s all.
I mean, people will copy other things. It’s going to happen. But it’s a bit peevy to find copies of your work with no accompanying text or reference to the source piece.