Which circumstance most directly resulted from the fall of the western roman empire?

The circumstance which most directly resulted from the fall of the Western roman Empire was that a rise of Christianity ensued coupled with the fact that Europe was in a disarray considering there was no imperial source left standing which would safeguard  certain trade routes. 

- Centralized government disappears 
- Loss of Greek and Roman learning and common language 
- Transportation and communication halts 
- Constant warfare and invasions 
- Cities abandoned as economic and political centers 
- Population becomes mostly rural and agrarian 
- Political, economic, and cultural face of Europe changes 
- Feudalism develops 
- Roman Catholic Church becomes a ruling power in Europe 

Government taxes ? i guess