Do you really think that if Putin got Ukraine he would be satisfied with that and stop?
He clearly never wanted all of Ukraine.
He clearly did. This is evident in his speech on February 21, 2022. You can find a transcript of it, translated into English by the Kremlin
here. Although the occasion was the announcement to recognise the independence and sovereignty of the Donetsk People's Republic and the Lugansk People's Republic, Putin made it clear in his 55 minute ramble that he regards the entire Ukraine as an inalienable part of Russia, that hiving it off as a separate entity was Lenin's mistake, and that he refuses to regard Ukraine as having ever been a nation in its own right. What exactly could the practical consequences of Putin's pronouncements be, other than the eventual reabsorption (in Putin's view) of all of Ukraine into Russia?
Some highlights:
"Ukraine is not just a neighbouring country for us. It is an inalienable part of our own history, culture and spiritual space."
"Since time immemorial, the people living in the south-west of what has historically been Russian land have called themselves Russians and Orthodox Christians. This was the case before the 17th century, when a portion of this territory rejoined the Russian state, and after."
"modern Ukraine was entirely created by Russia"
"When it comes to the historical destiny of Russia and its peoples, Lenin’s principles of state development were not just a mistake; they were worse than a mistake"
"Soviet Ukraine is the result of the Bolsheviks’ policy and can be rightfully called “Vladimir Lenin’s Ukraine.” He was its creator and architect."
"Let me repeat that these territories were transferred along with the population of what was historically Russia."
"Ukraine actually never had stable traditions of real statehood."
"A stable statehood has never developed in Ukraine;"