The Soviets controlled the State.
Contrary to belief, they were only willing to sacrifice the lives of their people. Their own hides were ranked too important to lose to a nuclear fallout.
The terrorists do not own a state. They have friendly authoritative regimes, but this is not quite the same. Those regimes do not control an army that will stand down at request. The terrorists operate independent of these regimes' wishes, nor do they fear the end of any life including their own.
They don't fear death. They fear not being able to reach paradise. Their weakness is not that complicated.