Older technology is often less vulnerable.
The Russians used vacuum tube radios in their MiGs & Sukhois. Impervious to EMP.
+1
Radiation-hardened computers are always going to lag behind the most recent civilian tech. They’re secret + they’re made of non-standard materials for milspec + the job they’re required to do just isn’t changing.
I guess there may also be advantages against hacking. Smuggling a virus in on a USB stick gets you nothing if the interface is a triangular floppy disk or something crazy like that.
A nuke base is the classic venue for “If it ain’t broke, don’t fix it”