Dialectics helps us understand and analyse the outcomes of historical decisions, as well as helping us analyse the potential outcomes of current decision making. It has an important focus on internal contradictions of a thing, which can help us understand why the class composition of the USSR led to particular historical outcomes besides the looming threat of nazism. It can also help us better analyse the components that resulted in the break down of Soviet socialism, the economic and social factors that led to the break down and why those formed intrinsic parts of the Soviet model. They were not imposed on it from without, they were historical conditions that required navigating by the communists at the time. Without dialectics we can miss the forest for the trees and avoid analysing the system for what it actually is and what it achieved and how those two things shaped and maintained one another.
In your example, why were the collectivisations forced? Why didn't the classes in the countryside voluntarily accept collectivisation? What was the shape and composition of the opposition to that policy and what were its results? What was the internal make-up of the party within those regions that led to their successes and failures? What could be done to avoid those failures in future? Were they inevitable? A dialectical approach would seek an immanent critique of the social system to analyse why history played out the way it did.