Feeling humiliated and driven to a point where one’s subjective feeling is that there is nothing left to lose, one does not need to be a madman to launch everything one has. Vengefulness is sufficient.
Note that subjective assessment of the situation is sufficient. Putin is dependent on nobody to come to such a conclusion, especially not the west, and why should he care anyway? Western war escalation enthusiasts apparently are willing to take the risk anyway or do not seem to understand this.
Where do you draw the line? Since you say this is purely dependent on Putin's subjective perception, and since you can't read his thoughts, would the logical consequence be that we need to just let him do unopposed whatever he wants to, out of fear that the smallest grievance could result in nuclear armageddon?
This, to me, seems what imperialism apologists are arguing for. Ignore the war of aggression, ignore the genocide, rape and murder of civilians, sacrifice Ukraine to protect Putin's ego, and just pray that his greed stops at that and that he won't continue given another opportunity.
There is probably a point where things go from happening gradually to happening suddenly. Very few can relate to the horrors of nuclear war or have the consequences of nuclear bombs in living memory.
Note that subjective assessment of the situation is sufficient. Putin is dependent on nobody to come to such a conclusion, especially not the west, and why should he care anyway? Western war escalation enthusiasts apparently are willing to take the risk anyway or do not seem to understand this.