And, arguably, the cold war was similar and it seemed to have a net positive impact on research and development for both nations... It was just a matter of who could run the longest.
Enough gear isn't networked or has fallbacks. C2 on the other hand, I'm less sure of. The French were so disturbed that they hacked the computers used by very senior people in the American military that they told the Americans so they would secure it better.
Far more likely is that both sides (other than Trump himself, maybe) know to default to standing down and absorbing the first blow then retaliate, if needed.
Oh, absolutely, total collapse is a fantasy.
How serious would the degradation be, now, that's an interesting question that probably literally nobody can answer.
But it's an amusing fantasy, and just connected enough to reality to not be in same nonsense realm as an alien eliminating all weapons or something.
Is there military crap? Sure. But part of the reason for double-price contracts is hardening and properly securing software.
Folks don't just sit at the Naval War College twiddling their fingers.
Which is, paradoxically, why massive numbers of traceable nuclear weapons + early warning actually make the world a safer place. (At least for major-power, global conflicts)
But tech espionage would fit nicely into a different, long-term game. There is (of course) a lot of work left to do spread the modern economy to the rest of their country. But if they can do that, they will have a huge population advantage and be the largest market in the world. Meanwhile they are already competitive (if not dominant) in manufacturing. So what's left? Tech.
If they can become competitive with (or even leap-frog) the West technologically, they'll really be the de-facto leader of the world in every economic dimension.
I've lately been having this fantasy, or day dream perhaps, where China or the US declares war on the other. The world cowers in fear at the impending catastrophic conflict, yet as the hours drag on, it becomes clear that nothing is happening. It turns out that the only net effect of the declaration of war is that 10 minutes later, every piece of military equipment either country has was bricked by the other's hackers and both militaries are now more-or-less sitting on their butts, twiddling their thumbs.
In which case the victory goes to Russia, I suppose.