One possible reason might indeed be that capitalism led to a faster innovation rate in the field of computing and chip manufacturing. Already in the 60s there was a pretty big gap between the computing capabilities of the soviet union and that of america.
The soviets then gave up their own architectures and just tried to reverse engineer the american computers. Needless to say that was a terrible decision but maybe there was no better alternative either. Imagine a country that relies solely on the computing hardware and software from 10 or 20 years ago. That alone might have been a reason why they couldn't keep up with the west.
The question is what ultimately led to the slower rate of innovation in the hardware industry compared to the US. As I said, I think it's because of capitalism. The possibility to get rich and invent your own stuff is just a huge motivator for people. Different people try a lot of things, fail a lot, but a few of them succeed. It's in a way similar to evolution.
On top of that the soviet union was a lot smaller in terms of their population compared to western europe + USA.