Late Stage Capitalism

I would not say without a fight. The Finnish Whites massacred the Finnish Reds (...and by extension anyone at all thought to be sympathetic to workers).

https://www.marxists.org/archive/serge/1930/year-one-sa/finland2.html

The victors massacred the vanquished. Since ancient times class wars have always been the most frightful. There are no more bloody and atrocious victories than the victories of reactionary classes. Since the blood-bath inflicted on the Paris Commune by the French bourgeoisie, the work had not seen anything comparable to the horrors of Finland. From the first shot of the civil war, “belonging to a workers’ organization in White territory meant arrest; to have been an official in such organization meant execution. The massacre of socialists reached such proportions that it ended by interesting no one.” At Kummen, where 43 Red Guards fell in battle, nearly five hundred persons were executed! There were “hundreds” executed at Kotka, a town of thirteen thousand inhabitants. “They didn’t even ask their names; they just led them away in groups.” At Raumo, according to a bourgeois newspaper, “five hundred prisoners captured on May 15 got the punishment they deserved the same day.” “April 14 in Toeloe, a suburb of Helsingfors, two hundred Red Guards were killed with machine guns ... The Reds were hunted from house to house. Many women perished.” At Sveaborg the public executions were set for Trinity Sunday. In the neighborhood of Lakhtis, where the Whites took thousands of prisoners, “the machine guns worked several hours a day.” “On one day alone two hundred women were killed with dumdum bullets; pieces of flesh flew in every direction.”

Finland was socialist for a short while before their revolution was drowned in blood by reactionaries. Also it's not just "Stalin convincing everyone", Finland independence or at least autonomy was one of the constant communist points since tsar crackdowned on Finland in 1890's.

Tbf the siege of Leningrad happened after.

And just to be clear, in case any historical revisionists are reading this: the Continuation War was not the USSR invading Finland, it was Finland invading the USSR alongside Nazi Germany.