Satan did not understand what he was doing. 


1 Corinthians 2:7-8

King James Version (KJV)

7 But we speak the wisdom of God in a mystery, even the hidden wisdom, which God ordained before the world unto our glory:
8 Which none of the princes of this world knew: for had they known it, they would not have crucified the Lord of glory.

It is amazing it was still a mystery considering it speaks about the redemptive plan in Gensis.