I am certain that the lapse that has permitted this man-child to confirm his strength and irascible command over the DPRK is one that will be admonished as a failure for years to come. Given that all of the member states of the UN Security Council have practiced and historically exercised self sponsored assassinations and infrastructure disruptions with the aim of regime change, someone fell asleep at the switch. Following the death of the second patriarchal despot to grace the peninsula the window was there, and they failed to open it. 
I am not a violent person, nor do I glorify state sponsored acts such as this and in most cases have decried such acts as the reasoning was not valid and was extremely immoral - this time I step that opinion aside for the security of nations who exercise peaceful ambitions. And I do believe, again, that he should have been eliminated at that juncture before he shored up his stranglehold on the nation.