A country has clear red lines for instance America has the Monro Doctrum this was used in the Cuban Missle Crisis - So when a Super Power feels threatend, it will react. Consider if China moved miltary bases to Canda and Mexico, what would America do?
The West has been openly advocating for Ukraine to join NATO Bucharest Summit 2008 (3rd April) . Russia informed NATO this has crossed thier red line - NATO expansion Eastwards was a direct threat to thier security, this was made clear to both NATO /Ukraine. v
Unfortunately, Ukraine is split country, Russian speakers in the East and Ukraine speakers in West, clearly shown when electrions have taken place. Russia felt it's Russian speakers were being discriminated by the Ukraine Goverment (see Stephan Bandera - Views)
In my view Russia is a Super Power, it is rich with resources which it can sell to Europe (Oil, Gas & Nuclear materials). It has the abliity to adapt. Which countries has been more effected by sancations imposed on Russia?