Because under the 1954 convention, “damage to cultural property means damage to the cultural heritage of all mankind”. So attacks on cultural heritage are a considered war crime. But treaties can only do so much. In the years since, conflicts around the world have rendered immeasurable damage to cultural heritage. A lot of it intentional. Like the Taliban’s destruction of the Bamiyan buddhas. And Isis’ attacks on ancient sites all over Syria.
“That cultural heritage is not only impacted, but in many ways it’s implicated and central to armed conflict. These are things that people point to that are unifying factors for their society. They are tangible reflections of their identity.”
And Putin has made it clear that identity is at the ideological center of Russia’s invasion: “I would like to emphasize again that Ukraine is not just a neighboring country for us. It is an inalienable part of our own history, culture, and spiritual space.”
“He thinks that we don’t really exist and they want to destroy all the signs of our identity.”(Source)