Greater Russia at the time of the First World War was an amalgamation of a number of different peoples, cultures and nationalities. There were many reasons, looked at from the point of view of natural boundaries, trade, safety and access for them to hold together for mutual benefit. Some of the states were landlocked or surrounded on all sides and required access to the wider world. Greater Russia, spanning the continental reach of Europe and Asia had a rationale for access to seas on each end of the country. Some of the states on the periphery were too weak, on their own, to withstand the pressure from potential powers on their borders. Yet all of these factors could not withstand the dispersing force of the different nationalities and cultures that could not find a psychological unity within the greater whole.
Sri Aurobindo observes: “…by union a State was created, so geographically compact, yet so large in bulk, numerous in population, well-defended by natural conditions and rich in potential resources that, if it had been properly organised, it could not only have stood secure in itself, but dominated half Asia, as it already does, and half Europe, as it was once, without proper organisation and development, almost on the way to do, when it interfered as armed arbiter, here deliverer, there champion of oppression in Austro-Hungary and in the Balkans. Even the assimilation of Finland was justified from this point of view; for a free Finland would have left Russia geographically and economically incomplete and beset and limited in her narrow Baltic outlet, while a Finland dominated by a strong Sweden or a powerful Germany would have been a standing military menace to the Russian capital and the Russian empire. The inclusion of Finland, on the contrary, made Russia secure, at ease and powerful at this vital point. Nor, might it be argued, did Finland herself really lose, since, independent, she would be too small and weak to maintain herself against neighboring imperial aggressiveness and must rely on the support of Russia. All these advantages have been destroyed, temporariliy at least, by the centrifugal forces let loose by the Revolution and its principle of the free choice of nationalities.”
Of course, the later history of Russia, as the Bolsheviks consolidated their hold and formed the Soviet Union, was to integrate, by force when necessary, those very free nationalities that had been set adrift earlier. The principle of free nationalities then once again re-asserted itself after the end of, successively, the 2nd World War and the Cold War, with the dissolution of the Soviet Union. The absence of a true psychological unity has made the repeated attempts at physical and vital unification eventually fall apart, despite various material and vital advantages that could be gained by the union.
Sri Aurobindo, The Ideal of Human Unity, Part Two, Chapter 30, The Principle of Free Confederation, pp. 266-267