In 2 Samuel 5, the elders of Israel come to David asking him to be their king. Up to this point, David has only been king over Judah but now Abner and Ish-bosheth, the two most likely kings of Israel, have both been killed. Now David is the most reasonable option for Israel and they covenant with him to be their king.
This passage describing the coronation of David as king over all Israel and Judah is widely recognized as the end of one phase of David's story; namely, the story of his rise to power. This story began back in 1 Samuel 16 when Samuel anointed David to be king even though he was a young boy. However, as the many chapters between that story and this story show, Samuel's anointing of David did not mean an immediate rise to power. After all, David was unknown and Saul was still king. In those chapters are story after story of David trusting God and refusing to force his own schedule or agenda. For example, David more than once has an opportunity to kill Saul, his political opponent, but he refuses to do so leaving it up to God to make him king as he promised. In fact, the story clears David of any culpability in the death of any of his enemies. While this certainly does not remove the blood and violence from the story of David's rise, it does show that David did not take his anointing into his own hands. He trusts God to fulfill his promises and this chapter of 2 Samuel records that God was faithful to those promises.
This is a continous struggle for us as the Church. God has promised us many things and we take those promises to heart and are passionate about seeing them fulfilled. But often we forget that they are God's promises to keep, not an agenda given to us to put in place. God calls us to be obedient and to trust him, not to make his plans happen for him. Does God want his Church to grow? Of course! But he wants it to grow through the work of his Spirit and the faithful Christ-likeness of his Church, not through some marketing gimmick. Does God want justice in our world? Yes, painfully so! But not by traditional means of power and might but by his Spirit and the mercy of his people. David's rise to power as king is a reminder to us that God does not need us to make his kingdom come; he only needs us to live faithfully in anticipation of it.