It all boiled down to miscommunication and a cascade of blunders:
The plan was to truncate a secretive exercise with the Australians near Indonesia, to cancel Vinson’s visit to Perth and then head the direction of the Korean Peninsula — meaning Vinson would be off North Korea by the end of the month.
Changing an aircraft carrier’s schedule is not a small muscle movement. Host nations expecting a visit from the mighty U.S. big decks have to do a fair amount of leg work to prepare for the visit. Furthermore, a good number of sailors had family flying out to Australia to meet their sailors. An Australia port visit is the holy grail for sailors on a Western Pacific deployment.
The easiest thing to do, PACOM officials decided, would be send out a press release announcing the canceled port visit — making it easier for families to get their money back from airlines and letting all parties know why the Vinson wouldn’t be visiting the Land Down Under.
So that was the plan, and a press release went out from the U.S. 3rd Fleet on April 8. Unfortunately, two hours before that went out, Reuters news agency published a story that said the Vinson Strike Group, which was visiting Singapore at the time, would proceed from there to the waters off North Korea to send a message to the rogue Korean regime, which is poised to detonate the country’s sixth nuclear bomb test.
As the media feeds upon itself, the Reuters story set off a frenzy as other media set up for going to war. The New York Times reported that president Trump was re-routing the naval armada as his latest show of force - despite the fact that it was a PACOM decision that he had nothing to do with. Yet panic set in across a number of countries even as the Vinson group was heading south, not north. All the Vinson group was doing was skipping a port of call at Perth, but everyone was freaking; and two days later, Ferret-top really lit things up:
"We are sending an armada, very powerful," he said. "We have submarines, very powerful, far more powerful than an aircraft carrier, that I can tell you."
The confirmation of the misleading narrative from the commander in chief — as well as the allusion to nuclear-armed ballistic missile submarines — sent the crisis into overdrive.
Countries immediately went on high alert, as the NorKs added fuel by promising thermonuclear war. While all of this was going on, it apparently didn't occur to anybody to check the actual location of the strike force until Defense News noticed that it was crossing Sunda Strait in Indonesia on April 17 - 3500 miles away from the Korean peninsula.
It looks as though there were blunders throughout the U.S. chain of command, exacerbated by media more eager to be first than factual.