The primary reason is Russian Imperialistic dream of restoring the Soviet Union.
Reasoning that a country can invade another country just because it feels insecure is insane. Not to mention that the border would become even closer, because now Russia would be expandee.
The baltic states are already close AF to primary population centers to have serios damage. Not to mention that Finland is also now NATO. Why didn’t Russia invade them also?
Takes a screenshot every minute and saves it