Can we say that the reasons for fragmentation in Russia and in the countries of Western Europe were the same?

Yes, the reasons for fragmentation in Russia and in the countries of Western Europe were the same, since fragmentation is a natural and natural process in all medieval countries. The main reasons for the fragmentation of states during the Middle Ages were:

1) an increase in the population, the construction of new cities, the development of individual regions, the ability to maintain their own army – all this reduced the need for central government;

2) each prince wanted to rule himself, albeit in a small, but his own state.