Bingo.
That's the $10,000 chip on the table in this little poker game. China can cripple NK with one single play. We can't force China to do something they'd rather not, but we can make it to where playing that card is their best option.
Meanwhile, Trump may be willing to play the Military Ace or he may not. China doesn't know and NK doesn't know. What past presidents have done, and what Obama did, was to signal that they would hold the Ace. If you are a Hyper Power but other players know the HP will only use the power *after* LA gets nuked, then they are free to act.
Pretty much with impunity, just don't fire nukes or otherwise poke the HP too hard. Which is pretty much what has gone on the last 20 years.
Trump, on the other hand, apparently doesn't suck at poker. He's using his cards to force China's hand. China is the key in this.
It's equally daring and brilliant.