Boiled frog?
They may be trying to desensitize world opinion by making a number of provocative baby steps, ending with the launch of a long range missile. The thinking may be, that with NK missiles going off all time, there's no threshold crossed, no point at which American public opinion turns decisively in favor of action against NK.
Remember 9-12-01? Who would have thought that the American public would become tired of the WOT this quickly and this easily?
My husband predicted a couple days after 9/11 that the Dems would start jumping ship within a week.