Because getting "made" doesn't apply to the afterlife.
Plus Costello retired when he was alive so it wasn't like he had an army on hand to avenge their boss. Nobody cared other than his blood relatives
SO you're telling me that if someone bombed Carlo Gambinos grave right after he had passed , that there would have been no retribution from the family and/or other families just based off of sheer respect many had for the man?
