For the same reason that you can make a similar-looking chair, but you can’t distribute a fuzzy copy of Star Wars. The char isn’t a copyrighted work.
An Eames chair is, we just have a really high bar for what is copyrightable in the physical world, and it seems pointlessly discriminatory.
there are also fan remakes of movies like this one. https://www.imdb.com/title/tt3528906/
I'm not a lawyer but this does seem like they're wholesale copying ideas.