When are you going to correct the title of the thread.
Perhaps who ever started it thought things would go another way.
Putin wants to negotiate. No joy.
Putin amasses and army on Ukraine's boarder. No joy.
Putin moves more troops into Belarus. No joy.*
Putin invades
* That point is particularly interesting. It was around this point that the USA etc said he would be invading. It was even mentioned that he had no choice as the alternative meant backing down. Moving troops into Belarus and the manoeuvrers there was a ploy that made it even more certain as a shorter run to Minsk.
So say that at the point where he actually invades NATO said sorry folks it's in your own interest to stay out of it. We'll probably never know detailed info on the discussions with the USA. One area seems to have been take your warheads out of Europe and back home. None in eastern europe etc. Ukraine never in NATO. More complicated though due to Dombas so he declares it independent and invades so saying they wont get into NATO probably wouldn't have helped. They'd want all of Dombas back probably in some independent form.
USA - Russia have had nuke discussions before. Never been clear that they really have reduced anything but they appear to have agreed something in the past.That leaves not in NATO and something different for Dombas. Sort all of that out and the war may not have happened not forgetting Crimea being declared as part of Russia. If it just concerned Crimea I suspect things would just finish up as being illegal and zero done about it. Ukraine is seems sees it differently. Changing it would mean a war with Russia.
That just leave Putin rhetoric about the USSR. It may just be intended for domestic consumption and not that he wants to take the lot back. NATO figures in that area anyway even as it is now and has been for a while. Not sure about Baltic states. No nukes in eastern europe is bound to figure.
So there may have been an opportunity for no war providing all could agree something or the other and in real terms we still don't really know what the end game is. If Russia feels it's caused the west and Ukraine enough grief they might just pull out. They may take over all or some of it even just the independent states they have declared. They may be defeated in real terms or just give up. Putin's replacement might pop up.