There's a very simple reason for focusing on the nuclear issue. Many, many issues are of supreme importance in one way or another, but if we blow ourselves up with nuclear weapons, no other issue is really going to matter. Quite possibly there would be no other human beings left to be concerned about anything else.
Theres a fraudulent root element of comedy in that we say things night after night as though they are rolling effortlessly from the brain and off the tongue, when in fact they are crafted over weeks and months and years.