I am usually the first and most vehement to laugh at conspiracy theories, but there might be something odd here. A feckless bureaucrat in Hawaii is one thing, but that *AND* Japan, with the Norks getting frisky...
Is it possible that there is an idea to have so many false alarms as to render people skeptical about real attacks?
My top guess:
This is cover for the Hawaii screwup. Someone with pull has convinced the Japanese to do this in order to provide cover for what happened in Hawaii. Someone doesn’t want us to look too carefully at what happened in Hawaii. Seems far too “convenient” for the timing of this event.
... removing tinfoil hat now.
My second guess is coincidence. They happen all the time. You never see a purple car on the road. But if you paint your car purple, you will start seeing them. Why? Because you are now very aware of purple cars.