There's a large tradition of having texts translated into Russian, whereas English speakers would very rarely read anything translated from another language.
"Tradition" sounds a bit funny knowing that a lot of Russian book publishing was/is published without author permission. Russian publishing isn't well known for following copyright laws :V
I'm pretty sure that Russian (Soviet?) publishers observed whatever copyright laws there were at the time. It's just that international copyright law is a recent phenomenon. USA is also a very late signatory of international book copyright treaties AFAIK.