For rebellion is as the sin of witchcraft, and stubbornness is as iniquity and idolatry. Because thou hast rejected the word of the LORD, he hath also rejected thee from being king.
Rebellion is like a very bad sin, like witchcraft. Stubbornness is also very wrong, like breaking rules and worshipping false gods. Since you refused to listen to God's message, He won't let you be a leader anymore.