Jamieson, Fausset and Brown on 1 Kings 16:21-22

21-22. Then were the people of Israel divided into two parts--The factions that ensued occasioned a four years' duration (compare 1Ki 16:15 with 1Ki 16:23), of anarchy or civil war. Whatever might be the public opinion of Omri's merits a large body of the people disapproved of the mode of his election, and declared for Tibni. The army, however, as usual in such circumstances (and they had the will of Providence favoring them), prevailed over all opposition, and Omri became undisputed possessor of the throne.