Now let us see another group of people. If we read the life of King Saul, we find that God' grace was upon him, and he became a king of Israel. God's spirit was upon him, he was a chosen man of God. But he did sin and disobeyed God. His sin does not look so grave as of David's, but God rejected him.
Reason is simple.
He never repented for his sins. He committed suicide and ended in hell fire. If we read the life of Judas Iscariot, we see the same thing. It brings forgiveness of sin and eternal life. This is the key.