Omri did what was evil in the sight of the LORD, and did more evil than all who were before him.
Solomon observes (Pro 28:2) that for the transgression of a land many were the princes thereof (so it was here in Israel), but by a man of understanding the state thereof shall be prolonged - so it was with Judah at the same time under Asa. When men forsake God they are out of the way of rest and establishment.
Commenting on 1 Kings 16:15-28
And he reared up an altar for Baal in the house of Baal, which he had built in Samaria. That he might not go so far as Tyre or Zidon; and for his wife's convenience also he built a temple in Samaria for Baal, and erected an altar there to offer sacrifices upon it unto him; so open and daring was he in his idolatrous practices.
But Omri wrought evil--The character of Omri's reign and his death are described in the stereotyped form used towards all the successors of Jeroboam in respect both to policy as well as time.