[chadash]

Two reasons:

- The actors are British (with the exception of one main character who is Swedish and speaks with a Swedish accent) so it's easiest for them to just use their own accents.

- For whatever reasons, they didn't want to film it in Russian, with Russian actors and subtitles. And they felt that foreigners trying to feign Russian accents starts to get comical. So they made the decision to just let actors use their own accents (they also felt that American audiences wouldn't process it well if they used American accents).

- I watched the show and the accents are annoying for about ten minutes until you get used to them and cease to notice/care

[haasted]

Gorbachev is played by a Swedish-Danish actor as well.

https://www.imdb.com/name/nm1399770/