The current agitation about the restitution of artistic treasures of all kinds to their original locations is usually presented as overdue justice for faults committed by European colonialism. In fact, this is a serious oversimplification. Conquering armies have always regarded works of art as legitimate spoil.
Swedish collections, for instance, are rich in objects from the collection of the Hapsburg Emperor, Rudolph II, taken during the Thirty Years War. These, however, were not generally the work of Czech artists but the possessions of an alien court that had based itself for a while in Prague. The modern Czech Republic does not pine for them too much, even when there is proof that they were actually created in Bohemia.
Modern attitudes to the legitimate or illegitimate possession of famous artworks can be traced to the European Enlightenment that blossomed in the late 18th century, and in particular to the impact made by Enlightenment ideas on the men of the French Revolution.