In the miniseries "Chernobyl" there's a minor character named Garanin. It's mentioned that he used to work in a shoe factory, then became Deputy Secretary who outranked a nuclear physicist. Was that kind of promotion common, or even possible in the Soviet Union?

I know it's a TV show, but I'm wondering how accurate that comment could have been. Was it really possible for any worker to be promoted into positions of power within the Communist Party? How would Garanin have managed that kind of rise? Or was that just meant to symbolize Soviet indifference to the accident and the incompetence of some of the higher-level politicians without being accurate?