Earlier quoted context omitted.
Owning huge amounts of land is uniquely antisocial in a way that owning huge amounts of other stuff isn't. If Mr Moneybags buys ten thousand paintings, we can always produce more paintings (and the rising price of paintings will push more people to take up careers in art). But if Moneybags buys ten thousand acres, the rest of us are ten thousand acres worse off in a way that we can't really fix.
Those are ten thousand paintings which the public cannot experience or enjoy! In many ways, the paintings are more precious, as they could go on worldwide tours, and be experienced by millions of people; most land has virtually no uniqueness, and cannot be shared.
The point here is to maintain a society and some things must come first, namely material things which paintings are not. Of course, art history shows us time and time again the vital importance of material sustenance in creating and preserving works of art. If you really care about art, you have to care about the material foundations that make rich and meaningful social livelihoods possible.