Russia did articulate that finlands entry would require a proportionate security response 

nukes on the Ukrainian border was  discussed wrt to to reduced time for nukes to hit moscow, and this was unacceptable

it's clearly multifactorial. ending neo nazi ideology and it's demilitarization, and stopping the shelling of culturally Russian peoples are part of the explicit goals

no doubt Russia now has the world's most capable military, thanks to Sanctions and NATOs war "practice"

I think Russia may not be "afraid", yet the devastating  WW2 reality they copped (which the yanks never appreciate) gives them a healthy respect that war is the last option to pursue