It suddenly dawned upon me late this afternoon that this is perhaps just a brilliant strategy by Trump.
Think of it like this: Fat Kim can't have that many missiles. They're just too damned poor. But he also can't resist firing one off when he gets his nose tweaked, either. Since pretty much everything they've ever tried to fire has blown up on the launch pad or else landed harmlessly in the drink, then in reality, we don't really face much of any sort of real risk from them lighting the fuse.
So, Trump just keeps pissing off Fat Kim, and Fat Kim keeps launching missiles that accomplish anything other than a fireworks show, and soon enough, Kim is out of ammo. And all it took Trump was a few tweets to get Kim to exhaust his supply.
Brilliant!