That is a question that needs some thought because Jesus was not only capable of great miracles, He also had a whole host of angels backing him up. Yet, when nailed to the cross, He allowed Himself to be treated like a lowly criminal.
It seems that staying on the cross, and not flexing His heavenly muscles, was his sacred challenge and mission. Why?
If any terrestrial human had the Lord’s heavenly power he would not have submitted himself to such humiliation and would have settled the score in a jiffy.
But that is precisely what separates God from humans—the infinite ability to resist egoism and the allurement of self-importance. So Jesus was fighting a deeper, hidden battle against all His corporeal/sensual (from the body’s) preferences.
We know from the New Testament story that the Lord of heaven was born on earth and given a human body of flesh. The human body (and flesh) comes with all kinds of hereditary flaws including flaws of character and various animal pleasures. Therefore, if Jesus were to battle against these worldly imperfections and inclinations and become victorious, He would succeed in making even His genetic human form equally divine with His heavenly soul. (This would give the Lord supremacy over all worldly evils and harmful intentions.) That meant the Lord had to stay on the cross to suffer the physical consequences and jeers. (Remember, Jesus was executed with two other criminals, who did not have the power to change their circumstances.)
What is a greater human temptation than to use one’s superior power over others to get one’s way? To not use such vast power would be a great sacrifice, but in this case it would also preserve human free will (as opposed to ruling others by compulsion and force, which always breeds inner rebellion).
Preserving human free will is to preserve a person’s heart and lifestyle, good or bad. This can only be a gift from a true God of love. Without free will, the human race cannot be offered the choice and desire for a more noble and rational love.
When Jesus died on the cross, what really died were the last vestiges of human self-love, giving birth of a higher, spiritual ideal.