I'm not suggesting this was the case here, but I am keen to find-out if the EBS in this case was genuinely an accident, or the EBS system was hacked somehow ?
Governor Ige was on CNN and said the cause had been determined. Somehow (in his words, "somebody pressed the wrong button," that could be literal or it could be a simplification) the alert got triggered during a shift change, which delayed identifying and fixing it.
It seems to me if it were that trivial to trigger it would be equally trivial to fix, but it's conceivable that because it's a serious alert with a likely short warning period that it could be made easier to issue than to take back. And this is an alert that's never been issued and never had to be taken back, so I can imagine a bunch of people flipping through disused manuals trying to figure out how to fix it, probably with a fair amount of blame passing going on.
Every job I've had, shift changes are the worst time for shit to hit the fan. You've got twice as many people in the building, but half as many on the job and sometimes unclear lines on just who's responsible for what because there's two people for every seat.
If the person who screwed up was basically out the door when it happened, their replacement needs to figure out what they did and how. And if they didn't realize it was a mistake and instead got the alert as they left work... Well, some people will immediately think they could have screwed up and go back in to see, and some people will be absolutely sure they didn't and join the panic, calling their loved ones is going to be more important than going back to work and clocking a few minutes for a job you don't think you'll live to be paid for.
Edit: A few other sites I go to have a lot of discussion on how differently this would have played out with a different president, because Trump was golfing and according to some reports didn't answer his phone (according to others he wasn't called, which I find more likely as I explain below). The three flavors of this claim:
A. If he'd been at work he would have authorized retaliation based on a false alarm
B. If it'd been some other president *they* would have authorized retaliation based on a false alarm
C. If it had been some other president, they would have been on TV allaying fears
A and B are both silly. This was a state level emergency broadcast system. Even if a president is utterly off his rocker like Martin Sheen in The Dead Zone, the joint chiefs and secdef aren't going to be on board with a second strike based on a state emergency alert when launch detection systems are quiet, and NORAD's not going to go to DEFCON 1 over an alarm not coming from their own systems.
C is... Well, maybe. It's true Trump has restricted media access more than the last several presidents, who have been perpetually trailed by a media circus wishing to happen, but 40 minutes is still a tight window. On 9/11, George W Bush hastily threw together his first TV appearance in a Florida school room where he'd been doing a photo op, and that took 44 minutes after the first attack.