Presumably: 1) the damage to statues can be dated - so we know roughly who did it, and 2) some of the damage is specifically targeted (like the article mentions

Presumably: 1) the damage to statues can be dated - so we know roughly who did it, and 2) some of the damage is specifically targeted (like the article mentions, the left/right hand damage would have meaning to Egyptians, but has far less context to supposed Christian attacks)