The people who survived were known to have contact with an Ebola victim. Duncan would not admit to it. His lie may have cost him his life.
I would guess that there were co morbidities such as hep c, or even hiv, or diabetes, etc....
This family's defensive lies also played a part in the delay of his treatment.
It is embarrassing to witness members of this family complain after all the risks taken on behalf of Duncan by so many people who bothered to care enough to try and save him.