What were the reasons for the establishment of feudal fragmentation in Western Europe? Appreciate this period in European history

A factor in this was the struggle with the Arabs. Karl Martell, when he learned that the Arabs had excellent cavalry, issued an order for this, so that during the period of work anyone would be given an insignificant palace. In the end, in this way a very large number of different countries arose, more abundant and more powerful than their own king. This became the factor of feudal fragmentation.