What does Isaiah 23:7 mean?

There can be no mistaking the shock and bafflement of Tarshish—and others—after hearing the great port city of Tyre could truly be destroyed (Isaiah 23:6). Like most in the world, Tarshish saw Tyre as a city full of life and excitement. Like many other port cities, Tyre would have bustled with activity as diverse travelers from far and wide made their way through the streets. The idea of such a place being gone would be hard to grasp. Tyre was an ancient city that had seemingly always been there. A human perspective makes it hard to imagine the disappearance of things that have been always around in our world .

To add to the prophecy's point, the people of Tyre weren't just traders. They became known around the world because they kept spreading out. It is likely they planted colonies at places across the sea to establish a foothold for more trade opportunities in more places. Tyre brought the world to the world. It was hard to fathom they were just gone. It would be as shocking as if one of the great cities of the world today was suddenly wiped from the earth, never to be heard from again in our lifetimes.