There are historical examples of similar situations. For instance, Pol Pot and his regime were responsible for the deaths of 1.5-2 million Cambodians, about 1/4 of the total population.

Things degrade due to the professionals, experts, and in general people-who-still-have-any-real-idea-what's-really-going-on either getting executed or fleeing. They get replaced by ameteurs, prisoners, kiss--asses ... all the usual suspects. Its shown well-enough in the show without being overbearing that you could call it a significant sub-plot.

Dramatic License; but there are limits.
Viddy this, O my brothers: two seasons from now, the executioners and enforcement gangs will all be under 14...