My mine reasoning is that:
1) on YouTube, there are many talks from American scholars, officials and intelligence talked about Ukraine, and predicted this conflict, even before the invasion, US insists that (although NATO doesn't want Ukraine) Ukraine has right to join NATO. US has trained Ukraine to be the frontline to fight Russia, knowing Russia would take action in response to NATO's plan;
2) US and UK are not worried the war would affect them directly, they are pushing to continue this conflict to bleed Russia economy and military, while other European countries who have a lot to lose want this conflict to end;
3) This war is not really about Russia and Ukraine, it is a war between Russia and US. To US's advantage, it is a proxy war where US does not need to participate directly. I believe US is more than happy to have this war than a direct conflict (which would result casualties and push back by voters);
4) Because this is mainly a US-Russia conflict, only US and Russia can stop this. US has shown no interests of deescalating the situation, instead, US has been using this as an opportunity to criticizing China, taking advantages of the situation. So far, US has not called for negotiation at all.
In response to your question, here is what Putin said:"It is not our plan to occupy the Ukrainian territory." (https://www.bloomberg.com/news/articles/2022-02-24/full-tran...)
I think Putin's stupid to do this, look at history of war, US's 20 years in Afghanistan, 20 years in Iraq, how can you invade a country? Maybe his plan was to get rid of Zelensky quickly.