Faced with a massive Assyrian threat, a desperate king turns to heaven for deliverance. The prophetic reply from Isaiah confirms that Hezekiah's heartfelt plea has been heard and accepted, setting the stage for a firm divine response against the enemy.
Although the message brings up the Assyrian ruler, it does not imply a direct address to him. Rather, there is a consensus that Hezekiah prayed to God specifically about Sennacherib, asking Him to intervene because of the blasphemous insults the enemy had spoken [רד״ק, מצודת דוד, ביאור שטיינזלץ].
This moment acts as a critical transition point in the narrative. It begins by describing God answering Hezekiah, but the prophetic style immediately shifts. The message that follows is framed as though God is confronting Sennacherib face-to-face. God argues with the enemy king, strongly rebuking him for his wickedness and his deliberate attempts to strike fear into the hearts of the Israelites [אברבנאל].