Was the development of feudalism credited to Charlemagne?
I think it is best to ay that Charlemagne did not develop
feudalism.
Feudalism means different things to different people, and there
is no good, broadly accepted definition of the word. But to see how
Charlemagne fit into the scheme of feudalism, we could look at two
different ideas of what it is.
One of these equates feudalism with manorialism. This is a
system in which unfree serfs, bound to the soil, work manors that
are possession of lords who derive their authority from a monarch
or higher lord and their income from the manor. This system
originated when Constantine I decreed that the coloni who worked on
villas were not permitted to leave those villas.
Another definition of feudalism is a system in which a weak
central government is supported by a series of feudal vows, such as
the commendation, with authority spread through the system to the
lowest level. This is a system that is ideally suited to an
environment in which critical problems, such as Viking raids,
develop locally and disappear too fast for a national military to
respond. This system originated soon after the death of
Charlemagne, and existed in France, the Holy Roman Empire, and very
briefly in England, along with other places.