His military point man, Mad Dog, is advising him to use his reputation for nuttiness (unpredictability and outright lunacy) to scare the crap out of the biggest danger facing the world today. A fat finger on the nuclear button (reference to financial sector keyboard inputting errors causing meltdowns, not being fattist).
The supreme leader (Big Un) knows the US is awash with nukes. So Trumpy doesn't have to prove he's got the potential to make S Korea an island. But what he does have to do is demonstrate he's prepared to use them at the slightest (or not even the slightest) provocation - and he's demonstrating this on universally recognised baddies who can't retaliate - at least no more than they already are. Namely an already defeated and largely grounded military in Syria (replaced by Russia), and the friendless (except by those lovely IS chaps) and relatively toothless Taliban in Afghanistan - who are going to get really really angry. Boo!
59 cruise missiles to flatten one air base in Syria?! Come on. 2 would have been overkill.
A MOAB (Mother Of All Bombs - ie one click short of nuclear) to take our a few tents???!
Trump is using expendables to send clear signals to NK (NuKe? The word was even invented for them) that he won't hesitate to remove the gorgeous one from power and that he will be the next target for a shower of cruise missiles armed with MOABs. Defend yourself against them if you can chubs. Can't huh? Not playing fair with lots of missiles not tipped with nukes?
So assuming this is the motive (and it's not hard to guess it is), then what's the end game?
That depends on Russia blustering but realising it's not personal, and China playing along behind the scenes, but overtly continuing to criticise US belligerence. They cannot be seen to let the US get away with this, but there can't be any doubt they don't want the Big Un to start a war. His only value to China is to prevent vast numbers of refugees from invading from the South by maintaining NK as a vast refugee camp at his expense. They really don't want him around any more than anyone else does (including his terrified citizens).
So my prediction is that China will let the US drop a MOAB on Kim Jong Un and then agree to take over NK with financial support from the USA in return for devaluing their currency... but will Japan and South Korea agree to this? It's out of their hands. They're never going to declare war on China if the USA isn't going to stand behind them. So bye bye Spratly Islands and the South China Sea. Small price to pay for removing KJU from the world.
Sounds like some sort of plan to me... oops did I give it away? Doh.