The good news of the kingdom that Jesus and his disciples preached had nothing to do with a ransom sacrifice. Think about it - how could it?? The disciples had no idea Jesus was going to die and were heavily disappointed when he did. The good news was only about loving God and loving your neighbor.
The ransom sacrifice was a tool used by Paul to help convert Jews to Christianity. Instead of sacrificing animals all the time, Jesus died once and for all. Therefore you don’t need to sacrifice anymore because Jesus was your sacrifice.
It is similar to when Moses instituted the Law. Instead of sacrificing your babies, you should sacrifice animals. It was a step up in knowledge from previous belief. (The Israelites still continued to fall back into the belief of human sacrifice from time to time).
The ransom sacrifice was a tool but it was never intended to be the cornerstone of the Christian faith. The Christian faith was all about dismantling institutionalized religion and having a personal faith with God while loving everybody as a brother and sister.