Charles Ellicott Commentary 2 Chronicles 33:13

"And he prayed unto him; and he was entreated of him, and heard his supplication, and brought him again to Jerusalem into his kingdom. Then Manasseh knew that Jehovah he was God." — 2 Chronicles 33:13 (ASV)

He was intreated of him. — 1 Chronicles 5:20.

And brought him again to Jerusalem. — The Assyrian monarch after a time saw fit to restore Manasseh to his throne as a vassal king. The case is exactly parallel to that of the Egyptian king Nikû (Necho I.), who was bound hand and foot, and sent to Nineveh; after which Assurbanipal extended his clemency to his captive, and restored him to his former state in his own country. (See Schrader, p. 371.)

Then. — And.

That the Lord he was God. — That Jehovah was the true God. (Compare to 1 Kings 18:39, where the same Hebrew words occur twice over.)