HI, the Bible is stories made up of people that are not real, the stories can be written anyway that the author wants them to be like. You would need to ask why the people of the Bible especially those in Genesis lives so long then they died? Perhaps the longevity had a purpose or was an example of something. This is all in the mind of the author. The people lived in order to make the characters more interesting since in former times things had to be born and they were not created. Longevity made them appealing and real so that the stories would be attractive to the reader.
