da purpose is to fulfill prophecies written in the old testament. these include a major increase in life span, the restoration of the kingdom of Israel that peter asked the Lord about in acts 1:6 and Jesus reigning from Jerusalem with a rod of iron. basically this is israel finally getting their promised kingdom governed by da law and the Messiah being their king.
why cant folks just believe the bible? it says a thousand years many times, therefore it means thousand years.