Additional reading if you're interested
https://www.leonardodicaprio.org/never-forget-the-stellers-sea-cow/
https://books.google.com/books?id=VtJY90BJ1yMC&pg=PA79#v=onepage&q&f=false
https://en.wikipedia.org/wiki/Steller%27s_sea_cow#cite_note-orcutt2003-26
https://www.theatlantic.com/science/archive/2017/04/pleistoseacow/522831/
https://coffeeandcreatures.co.uk/2019/08/29/stellers-sea-cow-facts/
https://archive.org/details/beringrussiandis0000fros/page/262/mode/2up
https://books.google.com/books?id=7pQgAwAAQBAJ&pg=PAfront#v=onepage&q&f=false
The hunting method used to kill steller's sea cows was similar to whaling (p20 quote 2.2 last link). So in case the way old people speak is above your head, here's what happened. Five men row on a boat and find a sea cow. One man stabs it with a harpoon, which has a rope connected to it. 40 men on shore haul on the rope, tiring it out, and then the men on the boat stab it to death with bayonets.
Due to their size and buoyancy, sea cows weren't good divers and inhabited coastal flats where they could graze. However, gently munching on sea grass and kelp near a horde of armed and starving sailors doesn't bode well. Their blubbery hot dog like physique also meant they were unable to outrun or hide from hunters. One account described the killing of a female sea cow. The male chased and repeatedly rammed the boat, and hovered by the shore while they sliced up his mate. He too was killed. Toward the twilight days of the sea cow, hunting parties would find herds of sea cows, and take advantage of their peaceful nature to stab them with harpoons. They would then let them bleed out and wait for the bodies to wash up on shore. This method was incredibly wasteful, and for every 5 sea cows harpooned, only one was ever eaten. The rest of the killed ones were lost.
However, the demise of the sea cow may be more complex. Their primary diet consisted of kelp and seaweed, a diet shared by sea urchins. Hunters and trappers quickly learned that sea otter pelts could sell for a pretty penny, and their population in the region crashed. The urchins which they preyed upon exploded in numbers, and hence the sea cow may have been out competed for food. Urchin destruction of kelp forests is a phenomenon also playing out in southern California due to the extinction of native otters.
In summary, a slow, peaceful sea mammal built like an oversized seal with the build of a couch potato and the double chins to match, without a fear of humans shuffled its way around the north pacific before being harpooned, deep fried, and starved as a side effect of otter hunting.
When Steller first sailed across the waters of the northern pacific, he shared the common belief that the sea was inexhaustible, and extinction an impossible phenomenon. However, that presumption was slowly debunked as the human population ballooned, coming into conflict with the natural world. The sea cow's demise can be seen as a reminder to own up to the consequences of our own actions, and that extinction isn't a long drawn out process. It can be quick and brutal, and it's happening with other species right before your eyes.
