When the feudal system succeeded on the local level, kings and emperors used the system on a much larger scale to strengthen their monarchies.
Explanation:
There was obviously a experimental period at first. Kings did observe how it was going to work out before putting that in practice in a larger scale, but eventually, they were quite happy with the results and kept using the model. If you think about it, it worked a lot like outsourcing. The lords were taking care of the lands and administrating them (they owned those lands), but were still servants and subjects to the crown and had to pay taxes to the king.
