Knowing more languages allows you to get perspective and info from more people. English has the most diverse perspectives because it is the de facto language of business around the world. Russian is spoken in... Russia. Knowing only Russian limits you to Russian information sources and perspectives.
While English is indeed very useful, Russian is spoken in quite a bit of countries as a first or second language (mainly in the former USSR).
"Basic English is enough for that" ?
I am amazed at the simplicity of the work you are referring to. Do they still pay a salary for that, or are these people supposed to work for free? Maybe they get paid through something like a Russian fiverr?