They never wanted the whole of Ukraine. That was just our propaganda fear mongering. They simply do not want a super power next to their border or their weapons. Remember the USA almost started WW3 with the Cuban Missile crisis? Same thing, here.

They wanted a buffer State/area. The west of Ukraine absolutely hates Russia, they could have never been able to hold it. Ever. This was obvious, sans propaganda. I mean, they stated as such. Did you not read about the Minsk II agreements that the UK and the USA help sabotage? If Ukraine had gone along with it then, then tens of thousands of Ukrainians would still be alive. Along with Russians, I guess.

https://en.wikipedia.org/wiki/Minsk_agreements

Source: Studied Geopolitics. Also, I can read past propaganda from both sides.