He's thinking of his legacy. Without too much psycho-babble about terminal urgency, He can't be leader of Great Russia like his heroes unless he recovers all of greater Russia. His recent scare over COVID caused him to accelerate a timeline or two. He's sick of Russia having the economy the size of Italy. He sees endless contraction and withering of what Russia was under the Soviets. So, fascist bully will fascistically bully and will seek to expand without or with bloodshed as best he can.
Cannot allow it to occur.