As a friend of mine said after taking a Russian history class, "The Russians have always been the Russians."
If you want to read a good book about Russian expansionism in the 18th and 19th Centuries, "The Great Game" by Peter Hopkirk is a terrific read. The usual pattern for absorbing Central Asia from the shores of the Caspian to the borders of China and Afghanistan was to send traders, then send soldiers to protect the traders while insisting loudly that they had no intentions of taking the area. Then the local commander would sieze control on some pretext of a threat to the traders or soldiers and, while Moscow swore that they hadn't planned this, they would proceed to absorb the territory. The British would be outraged and the Russians would swear it wouldn't happen again. Then traders would start moving into the next khanate.
Or as Churchill put it, “I cannot forecast to you the action of Russia. It is a riddle wrapped in a mystery inside an enigma: but perhaps there is a key. That key is Russian national interest.”