Even ruthless Russia's military capacities are
not unlimited, even if facing the Europeans only, without the US.
Lets not make them bigger than they are. They are big, but not THAT big. They can do what they now threaten to do.
To attack North and Middle and South Europe itself, that then again is another ball game, even with NATO now being the weakest ever. The huge Sowjet tank armies like in the cold war, are a thing of the past now, like huge numbers on Western sides are. What they can and would do is hybrid and cyber warfare instead. to throw Europeans off their feet and keep them busy with things in their own households. That way, they cnanot get into Russia'S way where Russia really aims at: the three small Baltic states, the Black Sea region, Balkans in parts, maybe, Ukraine.
I doubt that even in the cold war the Sovjets ever seriously planned to conquer central and Western Europe.