I recently seen a doentary on Kind David and his conquests and journey. I was wondering about David after?

Let me guess ' Simcha Jacobovici? There are "doentaries" which start with the bible or torah and attempt to find cirstantial evidence that allows them to declare their scripture as fact. In reality, there is scant evidence that David reign was anything like the biblical description and only a bit of evidence that David existed at all beyond his role in jewish mythology. That said, the writers of the torah certainly knew the significance of Jerusalem because they were the ones who wrote the Abrahamic myths. And note that there is no evidence that Abraham was a real person.