The answer
Because during Christ’s time on earth, He never fully revealed His divinity. At times the devils would declare, “You are the Son of God!” And then the Lord would conceal His divinity. Therefore the devil was confused, because he would see Christ at times performing miracles, and then at other times he would see Him crying, and hungry. Thus, it was only when Christ descended into Hades through the cross, to free the souls of the righteous, that Satan knew the identity of our Lord Jesus Christ.
H.G. Bishop Moussa