He knew he was God
From Sensus Plenior
2Ch 33:13 And prayed unto him: and he was intreated of him, and heard his supplication, and brought him again to Jerusalem into his kingdom. Then Manasseh knew that the LORD he [was] God.
He is knowing ידע
Manasseh 'causing to forget
that כי the Son of God's כ creation י
Yahweh - the I-am
he - הוא the 'not understanding' ה word ו was separated from the Father א
the Elohim - God אל separated from his people ים by ignorance ה