Eggs and Jesus

I’m having some serious problems understanding many things about Christianity, but this one may take the cake. It’s also somewhat timely since Easter has only recently passed. What is “dying for our sins?” Who decided this act has any significance whatsoever? The crucifixion was going to happen. If you believe in any semblance of free will, it seems obvious that Jesus was killed by the people. Was it an act of convenience? “Sure, I could save myself, but I want to die for your sins!” The whole thing is a spiritual game of Calvinball; why is it surprise that a man-god can triumph in this game in which he invents the rules as he goes along?