Since the USSR/СССР was so multicultural and linguistically diverse, with, among other countries, Kazakhstan, Mongolia and Estonia inside of it, was it seen as an asset to be bilingual or multilingual? What about English; was speaking English seen as an important skill to have?
Just a note: Mongolia was never in the Soviet Union. That said, the foreign language of choice for every educated person in Mongolia was Russian.
To put it simply, speaking Russian was an important skill to have. Depending on the time period you're discussing, anywhere between 60 and 75% of the USSR's population spoke Russian as a mother tongue. Both early and late in the Union's history, there were pushes for more focus on native languages. But Russia was BY FAR the most populous and influential SSR. Additionally, most of the USSR's territory had been incorporated into the Russian Empire for quite some time (and they never had the most progressive language or minority policies), so most of these areas were accustomed to using Russian to some degree.
To this day, Russian is a lingua franca in the region (note: this is definitely NOT true in the rest of the former Warsaw Pact, and is not universally accepted/spoken in places with political problems with modern Russia, like the Baltics, Georgia, and Western Ukraine) and a large Russian diaspora remains all over the Former Soviet Union.