‘Assa’ is about the
end of the Soviet era and the coming of Perestroika youth. I haven't seen ‘Chernobyl’ yet, but I doubt I'm gonna see many Perestroika youth among the people at the plant.
There were a lot of movies in the late 80s and the early-mid 90s about the life of lower-class people in the crumbling USSR/Russia of that time: from simple depressing realistic depictions to surrealistic transgressions, simply because all these kinds of expression became permissible. ‘Assa’ is essentially a fantasy about the zeitgeist. USSR functionaries weren't forgotten of course, but their portrayals flipped upside down—there isn't a single point of view on the Soviet time, and ‘Chernobyl’ likely just has a different perspective.
I'm gonna bet, though, that execs in ‘Chernobyl’ are close-ish to Krymov of ‘Assa’, at least as I will see them.
By the way, funny thing: in a podcast by Russian cinema critics on Western films about Russia, someone remarked that no matter how much effort the crew puts into researching details, something always gives away the fictional and foreign nature of the work. In ‘Chernobyl’, one such moment is when a woman goes against a committee of bureaucrats and tells them how wrong they are. (Again, IDK what actually happens in the scene.)