For God so loved the world, that he gave his one and only Son, that whoever believes in him should not perish, but have eternal life.
The thought in focus here is the sacrifice of Christ.  Such is the nature of sin and rebellion against God, that only God could extricate fallen humanity from the morass into which they had fallen; and God could do it only at awful cost in the giving of Jesus as an offering.  Note the significant shift of titles.   John 3:14 spoke of the Son of man; here Jesus spoke of the Son of God. No MAN could have died for all men; only God in the form of man could have done it.  The highest angel in heaven would not have sufficed to provide such an offering as Jesus.