The usual explanation for the coming of the kingdom of God in the NT runs along these lines: God is king in heaven, and there his will is fully done. But in the NT, his reign begins to come on earth “as in heaven.”
This observation is correct and provides vital insight for understanding the NT’s gospel and NT theology more generally. But we need to add two caveats.
(1) This world is the sphere of rebellion, but that does not mean that Satan and humanity operate outside divine concern and restraint.
(2) Thus, the coming of the kingdom preached by John, Jesus, and their followers was not a matter of God alone ruling on earth. It was also about humanity again becoming enthroned according to God’s original design. When humans return to their thrones, they will be the glorified human image-bearers God intended.
And then God’s commands will be done and his name hallowed, when his earthly kingdom on earth is restored to his vice-regents:
The saints of the Most High will receive the kingdom and will possess it forever……the Ancient of Days came and pronounced judgment in favor of the saints of the Most High, and the time came when they possessed the kingdom….Then the sovereignty, power and greatness of the kingdoms under the whole heaven will be handed over to the saints, the people of the Most High. His kingdom will be an everlasting kingdom, and all rulers will worship and obey him.