It would be between increased population, a steady stream of agricultural production, and technological advancements. As for the most important one of those three; that would be agricultural production.
The church played a very important role because it was "all around" in medieval times. On the level of almost every village there was a church and a priest which helped spread the word of the christian god. Through this, almost every person down to a villager somewhere in a village in Europe was able to come to church where people gathered on Sundays and hear new information and educate himself on various things related to faith and religion.
9 is an odd multiple of 6
