In USSR censoring of art was done by Ministry of Culture. Special committee reviewed performers and made a decision if they are safe for society (bring the right message) or not. Possible messages to be banned for: anti-socialist or anti-communist, religion (USSR is still atheistic), oversexualisation (sex was not banned but was considered "private matter", what happens in the bedroom - stays where), violence, drugs etc. Also performers could be banned for taking part at wrong demonstrations or scandals. After review performers was designated to official "safe" or "unsafe" lists for all country. In fact this reviewing procedure was standard for every art (movie, literature, songs, paintings...), soviet and foreign. Just a standard censoring for "maintaining society's health" so to speak.

So don't think that western culture was totally banned. Well, yes, it was in 1930-1950. But later Iron Curtain became much less iron and people danced with western music at the discos, read western literature and all that. Only with things which were officially allowed.

As for the music video - why not? It had to happen sometimes, Détente and all that. And Boney M was really popular in USSR.

(I'm not very good at finding english sources, all this come from history classes. But if you want, I can try to find something.)