Well the meaning is slightly different.
Many people have had their lives taken.
Many people's lives have been taken.
Look at where the が is attached to and it shows where the focus of the sentence is. In the first, the focus is on the people. In the second, the focus is on their lives. To answer your question of "shouldn't it be," it's a case of what the writer / speaker wants to focus on.
It's worth it to note the difference in usage has a slight nuance difference as well, I think.
PersonはXをされた usually expresses more of a negative feeling than simply saying
PersonのXがされた because if the person is the subject then there's more impact that it happened to a person and not an object.