Why was a cross chosen for Christ to die on?
Jesus stated, "When you lift up the Son of Man, then you will know that I am He, and I do nothing on My own initiative, but I speak these things as the Father taught Me" (John 8:28). Jesus not only predicted his death upon the cross, but he points out that this death would cause people to realize that Jesus was acting and teaching by the authority of God the Father. No one would choose such a cruel death as crucifixion; yet, Jesus voluntarily went to that death, knowing what he would face. "For this reason the Father loves Me, because I lay down My life so that I may take it again. No one has taken it away from Me, but I lay it down on My own initiative. I have authority to lay it down, and I have authority to take it up again. This commandment I received from My Father" (John 10:17-18).
However, Jesus also said in John 8:28, that his death on the cross will prove that Jesus is God. This is perhaps more subtle. Jesus proved repeatedly that he had vast power: he calmed storms, healed the sick, and raised the dead simply by his own say so. Imagine the greatest comic book superhero and realize that Jesus was someone greater. Yet, Jesus never used his vast power to benefit himself, even while dying on the cross. It wasn't that Jesus was powerless. "Or do you think that I cannot appeal to My Father, and He will at once put at My disposal more than twelve legions of angels?" (Matthew 26:53). Yet, Jesus instead chose obedience (Matthew 26:54). Name one human that you think could have that much power and not use it for his own benefit. We even acknowledge that "power corrupts and absolute power corrupts absolutely." Jesus' restraint on the cross proves that he is greater than human beings.
Jesus' death upon the cross also proves to us just how much he loved us. "And I, if I am lifted up from the earth, will draw all peoples to myself" (John 12:32). Death on a cross was the cruelest method devised by men in that era. Even though Jesus was innocent of all wrong, he willingly underwent this death in order to free men from their own sins. "For one will hardly die for a righteous man; though perhaps for the good man someone would dare even to die. But God demonstrates His own love toward us, in that while we were yet sinners, Christ died for us" (Romans 5:8-9). We are drawn to that powerful example of love. "By this the love of God was manifested in us, that God has sent His only begotten Son into the world so that we might live through Him. In this is love, not that we loved God, but that He loved us and sent His Son to be the propitiation for our sins. ... We love, because He first loved us" (I John 4:9-10, 19). A death in his sleep, or by accident, or even by violent warfare would not show the depth of Christ's love as his willingness to allow himself to be put to death through torture.