The people killed must have outlived their usefulness, or succumbed to debilitating illness.
You actually sound like you are cool with that.
Maybe they weren’t your adored great grandparents who were crazy about your dad and loved him more than life.
All I mean is that Mauthausen wasn't strictly a camp for extermination. It was slave labor, making, among other things, rifles for Himmler's SS. Himmler was a poultry fancier. And that's how he treated the Jews...like livestock. Produce while you can, and be killed when you no longer produce. Simply a fact of the Holocaust.
Sorry, if you took it personally.