You don’t think they did because you think is it too complicated?
Funny thing, the same thing was said about them having missile technology or fission capability.
The finest scientists the world had ever seen took another 7 years to produce a Fusion bomb here in the USA. No, I don't think second rate North Korean scientists are going to be able to replicate that work in less than a year.
Fat little idiot boy god-king is just lying again. His people do not know how to make a Hydrogen bomb.