Seem whenever a new US president is elected Putin tests to see how strong they are to his military advances and aggressiveness.
I wouldn't be surprised if the US starts building up forces in Ukraine close to the disputed region.
Putin is pushed and driven by super rich business people in Russia and they push and promote taking over lands which would be an advantage to their business ventures, lands that are not in possession of Russia but could be.
Then Putin gets a kick back making him rich.