Comment by kiba
One place that I see this happening is the Ukraine/Russia conflict where just because there hasn't been a nuclear exchange yet, people assume that there won't be, and keep pushing the line on acceptable escalation (on both sides -- Russia in starting the war, and the west in defending Ukraine). No we've got western tanks on the ground in Russia and Ukrainian drones bombing Moscow and who knows what is going to be the triggering event. 75 years of MAD doctrine thrown out the window and now we're deep in uncharted territory.
No, this is because Russia don't want western military aid in Ukraine, which is why they make threats to deter the west from sending aids. We also know what is their nuclear doctrine. Hint: Unless NATO invade Russia, nothing will happen.
The west nor Ukraine aren't interested in collapsing Russia as a state. Frankly, it's more likely that the continuation of war in Ukraine will collapse Russia.
The collapse of Russia could lead to nuclear war, misplaced bombs, or other calamities. After the collapse of the USSR, the West took great pains to ensure that the bombs outside the newly formed Russia didn't fall into the wrong hands.
There could be a replay of that scenario, but with an openly hostile and fragmented set of former-Russian states that won't allow Western "interference".