How to steal photos off someone’s iPhone from across the street
nakedsecurity.sophos.com
nakedsecurity.sophos.com
'One guy in a bedroom for 6 months' is a level of resourcing a nation state can easily obtain. It's also one Apple should be capable of obtaining as well.
Really the best way to prevent state level actors from developing exploits is to hire and repatriate or assassinate their talent. Seems to work for nuclear secrets.
I think you might be underestimating the technical sophistication of the intelligence agencies of many foreign powers (including the UK, China, Russia, Israel to name a few).
It tends to get used for nuclear secrets, but it doesn't seem to be as much effective at that goal as it is at providing a momentary salve on the feelings of impotence that go along with not having an effective method for that goal.
The only thing that really seems to work in that regard is altering the (international or domestic or both) political context to remove the motive for seeking the nuclear weapons technology in the first place, whether by externally-imposed regime change (Iraq) or a combination of resolving international tensions and domestic government transitions (Argentina/Brazil).