TLDR: Kennedy insisted on a pass code in 1962. Strategic Air Command prioritized expediency over security and set the “default” password to “00000000” as described in the nuclear launch manual. This code was (probably) not changed until someone made the information public in 1977 and a more secure procedure was implemented.

I mean the majority of security around nuclear weapons is physical. Both in access and also in the ability to transport/use it. They aren’t exactly small, they aren’t easy to transport, they aren’t easy to get access to, and once you get one, they aren’t exactly easy to use. If you went through all of the above, determining the password wouldn’t take long since presumably you’d have full physical access to the system being protected by a 1960’s era electronic security.

comment about luggage combination here