Yes, many fish do die in the wild, or shortly after being removed from it.
98% of marine fish headed for the aquarium trade die within a year in the Philippines (mongabay.com)
Analysis: U.S. Pet Trade Imports 6 Million Tropical Fish Exposed to Cyanide Poisoning Each Year (biologicaldiversity.org)
Fishing With Cyanide | Hakai Magazine
Aquarium Trade Kills Millions Of Tropical Fish Each Year - The Dodo
Even if the stats are off, you get the idea. It ain't so romantic keeping wild fish, when you understand how they got to the bag you took them home in.
A good read on how little anyone in the trade even cares. Google the following paper:
A Systematic Review of the Ornamental Fish Trade with Emphasis on Coral Reef Fishes—An Impossible Task
Ever visit a wholesale facility, or shops that import fish each week? Same thing, millions die from the stress of simply being netted, and transported to another retail or wholesale facility somewhere. Then add in the disease factor, oops. I have seen entire shipments wiped out from one thing or another. Nasty business it is.
Fish die, lots of them, countless millions, long before the massive die off from the hands of ignorant hobbyists, such as the ones in this story.
It's just a simple fact really, as humans we kill tropical fish for our selfish pleasure.