On the other hand, maybe destroying priceless art is a more effective way of sending their powerful relatives a message than, I dunno, reaming them out over Thanksgiving dinner.
If the human race goes extinct due to global warming or whatever reason, at least we left these artifacts behind.
People who do love and adore fine art are not limited to the super-rich (this was after all on public display), but I bet it cuts the super rich who can afford to hang originals on their bedroom walls a little deeper than most.
That said, I do know I'm not normal in many ways, perhaps more people than I assume care about originals.