Master Sun did not rush back to the Eastern Land, and first arranged various matters on the Red Clan Barbarian Continent properly. In the Sunset Country besides his cause and effect with Aunt Doris, there was one more person involved: Joel George.
Master Sun made some secret arrangements, and Joel George became like a seed, spreading some influences. These influences would not seem significant in normal times, but once Sunset Country faced a crisis like the division of faith in Boneset Country, they would gradually come into play, creating a situation as if a single spark could start a prairie fire. This was not just an incidental "idle move", but part of Master Sun's plan.