While I personally agree with this Realpolitik view, I don't believe it's actually universal among leaders. Many things that have happened historically did because leaders felt some grand moral imperative (national unification, stopping an atrocity, helping one's close ethnic allies in a defensive war, offensive "defences" when the momentum felt like it was being lost -- take your pick).
A moral imperative (although one rather out of place in the 21st century) seems to be behind Putin's actions, IMO. Restore the glory of the Russian empire, practical barriers to that will be ignored. It just must be done, for the sake of itself. Righteous causes eventually sort themselves out, right?
Which brings me to the sanctions. I've not actually seen much discussion on whether sanctions against Russia will achieve Western geopolitical goals. Much of the discussion is presently framed as a moral imperative. We must act to punish Putin.