> Why disable one critical crew member needed for a submarine's launch, when you can kill him, the entire crew, and everyone in a 10-mile radius with a single nuclear warhead?

Because you don't have enough of them...

You can't win against a nuclear state with 100+ ICBMs unless you strike first, or do a beheading strike.

USSR had really no defensive plan, as was found after the fall. They really bet all on "firing all your guns, before enemy can destroy them"