Complex sentence: Richardson labored to show the villagers a way that they could comprehend Jesus from the Bible, but the cultural barriers to understanding and accepting this teaching seemed impossible until an unlikely event brought the concept of the substitutionary atonement of Christ into immediate relevance for the Sawi.
Split into simpler sentences: Richardson labored to show the villagers a way that they could comprehend Jesus from the Bible, but the cultural barriers to understanding and accepting this teaching seemed impossible. But then unlikely event brought the concept of the substitutionary atonement of Christ into immediate relevance for the Sawi.