Albert Barnes Commentary 2 Samuel 15:3

"And Absalom said unto him, See, thy matters are good and right; but there is no man deputed of the king to hear thee." — 2 Samuel 15:3 (ASV)

Absalom's strategy was to flatter each person by pronouncing a favorable verdict in their case, to stir up a sense of grievance and discontent by criticizing the king for his negligence in trying the legal cases brought by his subjects, and to suggest a sure and easy remedy for all such grievances: making himself king.

He combined these tactics with great charm and courtesy, which his handsome appearance and high rank made all the more effective. This was how Absalom won the favor of the people, who were as shallow and fickle as he was.