The point is that copyright doesn't apply to someone's image or likeness - that's trademark! Copyright only applies to a work itself (at least in the US).

A deepfake Elvis video of a song that he didn't write would be subject to copyright by the original author of the song and to trademark by the owner of Elvis's likeness. However, it seems plausible that such a trademark claim might fail because (among other things) it should be apparent to a viewer that it isn't actually Elvis.