Unless I’m also having an off day, the article is just really confusing. It makes sense to me that Italy would want the base back because it would be like selling a framed painting to Hitler and getting only the canvas back when it was returned. (Hitler, amirite?)

It’s probably a pretty nice base. Probably custom made for the statue shortly after it was unearthed, and probably the sort of thing that art historians would care about keeping together with the sculpture for art historian reasons.