Trump looks like a big talking bluffer to the North Koreans. They might change their minds once we start doing things like moving US dependents and Civilians out of Korea and increasing weaponry and support for US troops along the border. Or blockading NK harbors from any trade. Or shooting down one of their missiles (but there is too much danger that we will miss). Same with economic sanctions— Trump threatens— looking to NK like he is bluffing again— and does notihing about the “real sanctions” he talks about like cutting trade with China (we all know how much that would hurt us) but not doing anything. Trump has created a concrete reputation as a bluffer. This also kills his ability to make a deal with NK, because again he looks dishonest and like he is bluffing.