They had Pravets computers and robotic arms in rural classrooms in places that didn’t have traffic lights, or English teachers. Chess and Math competitions as well, were accessible everywhere. Those were all self-feedback mechanisms that are cheap but allow an interested individual to iterate infinitely to reach advanced levels. Even if only a tiny subset of any population has the cognitive surplus to meddle with programming and math, they had easy access to fulfill that and be found. In the US, schools enable that with sports, which monetize as entertainment venues. In the Eastern Block they had that with brains. As soon as the stupid restrictions on travel were lifted, the brains knew to leave the other restrictions and immigrate to places that reward cognitive surplus.
Intelligence builds with reinforcement learning on context that gives you feedback - which makes it easy to iterate on. If you’re not making those types of games/tools/systems available to kids, you are going to lose that generation to more attention grabbing stuff like Youtube or sports.