Albert Barnes Commentary 2 Kings 15:37

"In those days Jehovah began to send against Judah Rezin the king of Syria, and Pekah the son of Remaliah." — 2 Kings 15:37 (ASV)

The recent invasions by Pul and Tiglath-Pileser had thoroughly alarmed Pekah and Rezin, leading them to set aside their traditional jealousies and form an offensive and defensive alliance.

They were anxious for Judah to join this alliance but distrusted the house of David, which had long been hostile to both Damascus and Samaria. Consequently, they formed a plan to transfer the crown of Judah to a certain Ben-Tabeal (Isaiah 7:6). He was likely a noble from Judah, perhaps a refugee at one of their courts, whom they could trust to join wholeheartedly in their plans (2 Kings 16:5 note).