That's well known in crypto history. "I want a thousand-megacycle computer! I'll get you the money" said the general heading NSA in the 1960s. The best they ever got from cyrotrons was a special-purpose device, not a whole computer. But they reportedly did get a gigahertz clock rate, decades before anybody else.

The trouble with cyrotrons was that you could make them fast, but you couldn't make them small. Not by IC standards, anyway. They have a magnetic component, which limits the packing density and makes fabrication by lithography very tough. So mainstream IC technology won out.

In the early days of computing, the military was way ahead of the civilian market, because the military was spending the money. In the early 1980s, the civilian market caught up, and by the late 1980s, the now much larger civilian market was ahead.