"The Wasserspiele of Bergpark Wilhelmshöhe are 300 years old, powered entirely by gravity, and entertaining tourists. As legacies for rich people go, there are far worse ones."
I think those gilded age people were still basing their beliefs on a very old idea of what wealth is supposed to be. The elite of Ancient Greece and Rome who would often fund public works projects. The gilded age industrialists really wanted to show the rest of the world how powerful they were. America wasn’t the same global power it was today and they were proving to the “old world” that they could rival them in beauty and wealth.
Modern billionaires have started to realize that if they controlled the government more than their predecessors, they could make more money. Their version of public works, museums, and gardens is a restructure of their role in society so they can become kings.