וַיֵּ֨לֶךְ דָּוִ֧יד וְכָל־יִשְׂרָאֵ֛ל יְרוּשָׁלִַ֖ם הִ֣יא יְב֑וּס וְשָׁם֙ הַיְבוּסִ֔י יֹשְׁבֵ֖י הָאָֽרֶץ׃
And David and all Israel went to Jerusalem—the same is Jebus—and the Jebusites, the inhabitants of the land, were there.
Radak
And the king and his men went to Jerusalem – In Divre HaYamim it says “And David and all of Israel went to Jerusalem…” (Divre HaYamim I 11:4) because now all of Israel were his men. Since he was now king over all of Israel he went to Jerusalem to conquer the citadel of Zion because they had a tradition that Zion was the head of kingship in Israel and only one who was king over all of Israel would conquer. Unto this day there had not been full kingship in Israel because Shaul’s kingship was not permanently established.