When you die, your family members can choose to have your Facebook page memorialized. Once they do, those privacy settings will stay in death the same as they were in life.

In a blog post earlier, Facebook explained their reasoning for the change:
Up to now, when a person's account was memorialized, we restricted its visibility to friends-only. This meant that people could no longer see the account or any of its content unless they were Facebook friends with the person who passed away. Starting today, we will maintain the visibility of a person's content as-is. This will allow people to see memorialized profiles in a manner consistent with the deceased person's expectations of privacy. We are respecting the choices a person made in life while giving their extended community of family and friends ongoing visibility to the same content they could always see.
So it's to introduce more Look Back moments, which Facebook seems to want to make it easier for grievers who might not have been friends with the deceased on Facebook.