Answer:
One driving factor of Soviet doctrine in nuclear developments that was not a driving factor of US doctrine was the concept of "massive retaliation." The Soviet Union adopted this doctrine in the 1950s, which held that any attack on Soviet territory, no matter how small, would result in a massive nuclear response.
In contrast, the United States did not fully embrace the concept of "massive retaliation" and instead adopted a doctrine of "flexible response," which emphasized a range of military options beyond just the use of nuclear weapons. The US also developed a nuclear strategy of deterrence, which sought to prevent nuclear war through the threat of mutual assured destruction.
Therefore, "massive retaliation" was a driving factor of Soviet doctrine and not US doctrine in nuclear developments.