What are the reasons for the formation of the USSR? What are the prerequisites for the formation of the USSR?

1) The reasons for the formation of the USSR were:
The formation of several republics on the territory of the Russian Empire, each was formally independent, each of them was headed by the Bolsheviks, so each of their parties wanted the unification of parties and republics.
The need to create a common system and thereby get rid of bilateral agreements.
The need to pool economic resources
The unification of the republics was supposed to help strengthen the state in the international arena.
2) Prerequisites for the formation of the USSR:
Economic unity;
Industry;
The people had the memory of belonging to a single state.