During the rebellion of Absalom, the ten tribes of Israel rebelled against David and the tribes of Judah and Benjamin, but once the fighting ended, Israel again supported David, and he needed to get Judah back in also,

So King David sent to Zadok and Abiathar the priests, saying, “Speak to the elders of Judah, saying, ‘Why are you the last to bring the king back to his house, since the words of all Israel have come to the king, to his very house? You are my brethren, you are my bone and my flesh. Why then are you the last to bring back the king?’ And say to Amasa, ‘Are you not my bone and my flesh? God do so to me, and more also, if you are not commander of the army before me continually in place of Joab.’” So he swayed the hearts of all the men of Judah, just as the heart of one man, so that they sent this word to the king: “Return, you and all your servants!” (2 Samuel 19:11–14).

David showed his wisdom in doing these things, but it seems that he should have replaced Joab long before this rebellion.

Was David a perfect man? No, but he always sought what glorified God, and what was best for Israel.