Still, that's because during the 1,000 year reign, there is no challenge to the throne as Satan is in the pit
Rev 20:1
And I saw an angel come down from heaven, having the key of the bottomless pit and a great chain in his hand.
2 And he laid hold on the dragon, that old serpent, which is the Devil, and Satan, and bound him a thousand years,
Then Satan is released and challenges the throne of Christ as it was so with David, By His son. This creation of God that went bad will challenge again.
Rev 20:7
And when the thousand years are expired, Satan shall be loosed out of his prison,
8 And shall go out to deceive the nations which are in the four quarters of the earth, Gog, and Magog, to gather them together to battle: the number of whom is as the sand of the sea.
9 And they went up on the breadth of the earth, and compassed the camp of the saints about, and the beloved city: and fire came down from God out of heaven, and devoured them.
10 And the devil that deceived them was cast into the lake of fire and brimstone, where the beast and the false prophet are, and shall be tormented day and night for ever and ever.
His reign does not end, it is only challenged and quickly done away with. Then perfection for ever comes as New Jerusalem descends from heaven and the Father makes his headquarter on Earth and specifically Jerusalem.