Trump is a populist and is politically naive.
President Trump is a Populist to a point, but his main purpose is the saving of Capitalism. And, he is a successful Populist, which one does not become if one is politically naive. I am disheartened by the political naivety of the alleged ''Left'' in fact, which is always divided and diverted, by the picking up of the false and stupid idea that Trump is somehow in reality a buffoon and politically inept moron, when nothing further could be from the case. I guess it's a revelation of the truism, that ''he whom the gods would destroy, they first make mad''...
If the US attacked North Korea, South Korea would be attacked and China would retaliate.
You assume that the US would attack first, or give the appearance of being attacked. You also assume that China is like Maoist China which came to the aid of North Korea in 1950-1954, and you assume that North Korea is the same too. Lots of assumptions.
In fact, North Korean strategic military doctrine emphatically points out that in the event of what they see as an inevitable war with the US, they would not be able to depend on anyone else to help them, and thus they think they must have the political will to defeat the US by themselves if they wish their political entity to survive.
But man is a fickle and disreputable creature and perhaps, like a chess-player, is interested in the process of attaining his goal rather than the goal itself.