(1) Most countries have a lot of concentration of population, power, wealth in a capital city, for instance Tokyo, Paris, London, etc. In the 1970s it was generally understood that this causes political instability and increases vulnerability to thermonuclear weapons, see

https://books.google.com/books/about/Dispersing_Population.h...

By the 1990s it was a forgotten cause: countries weren't willing to give up a few points of efficiency facing the fierce competition and the cold war was over.

(2) Russia was particularly extreme at that time because, under Communism, Russia was transforming from a mostly agrarian country with spots of advanced thinking (Russian Futurists, Konstantin Tsiolkovsky) to an industrial powerhouse that could challenge the United States. Ironically if there was anything about the Stalin years it was that Russia was highly successful at capital accumulation and around that time many "non-aligned" and less developed countries like India were hoping the USSR could help them do the same.

Karl Marx was mainly interested in the advanced industrial "core" but Lenin was more interested in "peripheral" countries that were exploited by the "core". The USSR was more about winning the international competition than it was about advancing the working class and the military threat from Germany, US and other countries meant the USSR had to develop as rapidly as possible so it reproduced an imperialist system internally with a division of labor that advanced industry around Moscow and a few other centers at the expense of the countryside, see

https://en.wikipedia.org/wiki/Kulak#Dekulakization

If you're interested in the spatial division of the world you really need to read

https://www.amazon.com/Modern-World-System-I-Immanuel-Waller...

and the rest of the four volume set it is a part of.

The Manhoff Archives: Color photos of Stalin-era USSR taken by a US diplomat