The Assyrian spokesman addresses the residents of Jerusalem with a calculated, rhetorical argument designed to completely undermine their confidence [מדוד ועד לחורבן]. He points to his empire's track record of military dominance, noting that no other god has ever successfully protected their land from Assyrian conquest.
Building on these past victories, the speaker draws a direct conclusion about God's ability to save His people. He issues a bold challenge, demanding to know why the people of Jerusalem believe their outcome will be any different. Since the gods of every other conquered nation failed to deliver them, he argues, there is no reason to think that God will be able to rescue Jerusalem from his grip [ביאור שטיינזלץ].