I can see where the North Korean's would consider such inflammatory speach by US president Trump as highly insulting and see it as a declaration of war.
Trump clearly has no idea what and who he is dealing with, North Korea in his estimation is a sore loser, and in need of some serious ass kicking, and faults previous administration for not taking firmer actions against NK. Trump is drunk with destructive power and is making it clear to the world that he is ready to unleash it.