Ironically DPRK would probably make the most money if they just ran honest banks and exchanges without the FATF and KYC nonsense, as a sort of refuge from regulation that island nations used to provide. There is massive demand and few options.
Unfortunately I'm afraid to venture too far into how/why I think it would work and being Virgil Griffith'd, and intentionally leaving it as a pure speculation on a hypothetical.
My guess is that despite the DPRK appearing to be independent (nuclear et al), it really is not. NK envisaged starting not just an exchange but a whole "deregulated/free" city but China prevented them from doing that.
They do have other free enterprises, for example see: https://en.wikipedia.org/wiki/Rason_Special_Economic_Zone
A random US Citizen cannot wire USD to NK. Their bank is not going to allow it. Their credit card company is not going to allow it. If you try to mail physical USD the USPS is going to confiscate it [1].
So, this leaves a US Citizen buying crypto on a KYC exchange and then transferring it to the NK exchange. Why? Just keep the crypto on the KYC exchange at this point.