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.