The hill offers the only view in England to be protected by an Act of Parliament—the Richmond, Ham and Petersham Open Spaces Act passed in 1902—to protect the land on and below it and thus preserve the fine views to the west and south. Two years before the wooded isle centrepiece of the view, Glover's Island (also known as Clam Island), was bought by a local resident and given to the Richmond Corporation (Borough) in return for the latter noting against its records that it and its successors would not develop the isle.
In hindsight it maybe should have also been obvious from the language alone. "Richmond Hill" feels a bit like saying "Rich Hill Hill" which is basically like saying "Wealthy Desirable Area."
BTW there is a linguistic tradition of “hill hill”. When new immigrants come to an area and ask the locals what that hill is called, the locals say “big hill” in their language. The newcomers call it “bighill” hill in their language. I forget the examples but this has happened enough in England that there are places whose names are five hills deep (Brythonic -> Latin -> Saxon -> Norse -> Norman).
One of my favourite quotes from the late Terry Pratchett:
> When the first explorers from the warm lands around the Circle Sea travelled into the chilly hinterland they filled in the blank spaces on their maps by grabbing the nearest native, pointing at some distant landmark, speaking very clearly in a loud voice, and writing down whatever the bemused man told them. Thus were immortalised in generations of atlases such geographical oddities as Just A Mountain, I Don't Know, What? and, of course, Your Finger You Fool.
https://en.wikipedia.org/wiki/Richmond_Hill,_London