Russians might not want to screw around with the Finns. It didn’t work out so well for them last time.
The idea that Finland defeated the Soviets an amazingly persistent myth. The fact is that the Finns did bloody the Russians' noses in the early phases of the war, but in the end the sheer weight of numbers (and some command reforms of the purge-ravaged Red Army)could not be withstood. The Finns sued for peace and in the Treaty of Moscow, ceded 11% of their national territory, representing about 30% of their economic resources, to the USSR. They had to give 75 locomotives and 2000 rail cars. They had to give ships and trucks. They had to give something like a third of their hydroelectric generating capacity and one of their largest industrial complexes. The war worked out very well for the Russians, except for the bunch of people killed. And when did the Russians ever care about that?
Hitler thought, based on the Winter War, that invading Russia would be a cakewalk.....not so much.