It is ludicrous to suggest that Putin threatening to nuke Ukraine is somehow the fault of NATO. If Putin launches nukes in aggression, it is Putin's fault. Stop wringing your hands in apologetic appeasement to madmen.
As for whose fault is what — honestly, would you care, if either Russia launches nukes or NATO does so preemptively, and then the other side inevitably retaliates, and our world dies in flames — would you really care whose fault it would have been? Would it really matter to you?
https://www.reuters.com/world/europe/russia-says-its-troops-...