In 2 Samuel 20, we see two aspects to David’s Kingdom. John Woodhouse reminds us that on the one hand God chose David and make him king over his old testament people, Israel.
God’s promise to establish his kingdom forever was clearly and explicitly made to David. The king in God’s promised kingdom would be a son of David (that was 2Samuel 7:12-16). And David’s own kingdom displayed something of the character of God’s kingdom.

But on the other hand, as Dr Woodhouse notes, David’s kingdom was not like the promised kingdom. David - like me and you - is deeply flawed. His failings made his kingdom unstable. He was not wise, powerful or good enough to establish a permanent kingdom of goodness, love and justice. His kingdom eventually displayed the weakness of all human communities.

We long for the day when God’s king will rule truely in heaven and we cry with the writer of Revelation, Come Lord Jesus.

2 Samuel 20:1 Now a wicked man, a Benjaminite named Sheba son of Bichri, happened to be there. He blew the ram’s horn and shouted:
We have no portion in David,no inheritance in Jesse’s son.Each man to his tent,[a] Israel!

2 So all the men of Israel deserted David and followed Sheba son of Bichri, but the men of Judah from the Jordan all the way to Jerusalem remained loyal to their king.

3 When David came to his palace in Jerusalem, he took the ten concubines he had left to take care of the palace and placed them under guard. He provided for them, but he was not intimate with them. They were confined until the day of their death, living as widows.