It had to be a man that would perfectly live according to the law of God. Our problem is, no man can do that. “All have sinned and come short of the glory of God” (Rom 3:23).
Seeing our plight, God in love sent His Son to be made flesh, and dwell among us. Being God, the Son of God could do two things that sinful man cannot do, a) live in perfect obedience to the law of God man had broken, b) offer Himself as a substitute in such a way that His suffering would remove man’s sin.
You see, only as a man could the Son of God be tempted, and only as a man could He suffer. And so Paul is able to write, “For since by man came death, by man came also the resurrection of the dead.” (1 Cor 15:21). This is why Jesus is the only one who can save you.