while i definitely understand and sympathize with your sentiments the way i understood it is that by collecting pieces of history makes him somehow cultured and important
think about it if your a billionaire you really have nothing else left to do in your life but try to get approval and acceptance from others who you believe to be above your humble beginnings so he is just trying to fit in and be a collector of history same thing goes for any objects that belonged to any murderous tyrant they still become valuable in the eyes of the bored rich people who have nothing better to do with their lives as time passes