Why did the ancient Russian people split into three peoples?

Regarding the general existence of the ancient Russian nationality, discussions are still taking place to this day, because in principle, the assertion about the existence of such a phenomenon is very controversial. It is more characteristic of the Soviet period, because in this way it was possible, in principle, to explain the modern unification of states by brotherhood and tradition. But if we still proceed from this point of view, then this could be influenced by a number of factors – the main of them will be feudal fragmentation, which determined the different development centers of a particular group of nationalities.