While everyone needs sustenance, there are often several adequate choices about how to get it and making those choices become a way of communicating to others. And communicating is an defining and seemingly valuable part of being human.
It’s not really weird and it’s not going anywhere.
At the time, salmon was the cheapest, most abundant source of protein. Poor people's food.
IIRC, lobster in New England was about the same.
So, novelty and cool factor, plus appeal to those looking for healthy options; some overlap with the faddish nature of trends in healthy eating.
poor people use wheat etc.
Mark Kurlansky's The Big Oyster has some great primary source research on the social status of eating shellfish through the years.
[0]: https://www.nytimes.com/2012/07/29/us/in-maine-fishermen-str...