This is an oft repeated myth. The US was far, far ahead of the Russians already to the point where they stood no chance of catching up. What motivated Star Wars

This is an oft repeated myth. The US was far, far ahead of the Russians already to the point where they stood no chance of catching up. What motivated Star Wars was that the US had been overestimating Russian capability since the 1960s by factors of 10-100, so by the mid-1980s they were actually worried about where they stood. Basically, the CIA had no idea what was going on, as evidenced by their complete shock at the collapse of the USSR. Reagan decided to spend a ton of money redressing an imbalance that never existed. Star Wars and less fictional technology such as the stealth bomber were so far ahead of what the Ruasians had that they actually risked destabilising MAD to the point where a Russian first strike could be a logical choice. So the decision was irrational unless the US thought the Russians were ahead of them.