Voiceover is much faster and cheaper to do than a professional dub, and can be done by a single voice for all characters. Since most cool movies / cartoons / series got to the audience in Eastern Europe through pirates, and pirates would only do voiceover, voiceover became a cultural norm for a while, even for officially released stuff. It has now shifted towards dubbing though. In the 90s, when the piracy was at its peak, there were several competing pirate studios in Russia that raced against each other releasing as many movies daily as possible. Some even employed simultaneous interpreters who would do the voiceover without watching those movies first, so listening to them was... an experience in its own right. One of those interpreters became a legend in the professional community and he claims to have done up to 8 movies daily at some point. He is responsible for infusing the Russian language with his translation of "holy shit", which is "god's diarrhea"