Ex, why do you continually conflate intelligence with rationality?
What about Putin tells you he's a rational actor? His willingness to invade countries at the cost of the greater economy? Crimea is hardly an investment, it's an added liability. It only serves to improve his standing among Russians. Temporarily. Until the true costs are weighed.
Say the troops are massing on the Eastern border to annex several Eastern Ukrainian regions. If he does this is it merely just another calculated response to Western/NATO aggression? And why then does nearly every other nation on this border heartily oppose any annexation whatsoever? Belarus, Lithuania, Estonia, Latvia, Finland, etc? Are they all Western Puppets?