Peter never know that Jesus had interceeded for him till He made him aware. how can we believe that someone has been sacrified for us if He did that come on earth to go through that torture? Also,it was because of how hardened our hearts are.

He had to be tortured for some(not all) to be moved by that and depart from their wicked ways. Others were also convinced by His word preached to them and some too were moved by the miracles He performed( many believed Him when He raised Lazarus from death).

He dead phycal death so there will be a mark to look upon any time we go way ward. His spiritual death was what closed the gab between God and His children.

His crusifiction comes in a package,so He cannot neglect some and accept the rest.