If newsies have said it, it's far from a secret.
And newsies have said the reason China isn't restraining North Korea is that China would rather even an unstable and flippy ally running North Korea than regime change handing control of the whole peninsula to the South Korean government, a close American ally.
That would put an American ally with a lot of American forces on the ground right on the Chinese border.
So why has no one tried the expedient of quietly urging China to replace the current, nutso NK regime with a sensible one, allied also with China, but with no nuclear aspirations and no inclinations toward trouble-making?
Or, in fact, has this been tried?
Meanwhile, Lindsey Graham is urging the availability of genuine military options, to destroy the NK nuclear program or even to destroy NK, if the president is forced to choose such things to preserve American security against a nuclear attack from NK.