IMO it isn't much about parasites, it is more a B2B sales tactics turned B2C, and turns out general public likes it. The Project Japan pitch in 1985 was targeting a group of japanese industry experts. It is this group of expert that says the salmon contains parasites hence the customer won't eat it. But in the 90s, after the striking the deal with Nichirei, they find that customer actually like the fatty taste of salmon, parasites wasn't a concern to most.
It's like facebook/tiktok pitching their platform to an HN crowd and we obsess over security, privacy, social bubble, vision and stuff, turns out no one give a damn. People like scrolling on the phone aimlessly. That's the fatty salmon
It's not the same at all. At first glance it might feel the same, but the structural questions are different. The fact that the Facebook does have privacy problems does not show that Atlantic salmon does actually have parasites problems in the same way that pacific salmon does.
In the USA fish for sushi is suggested by the FDA (and required by local law in some places: New York city comes to mind) to be frozen to -31F for 15 hours (or -4F for seven days), specifically to kill parasites. Given that virtually all salmon in the US has been frozen, I wouldn't worry about parasites in salmon sushi here.
This tracks with the historic consumption of other species that are also hosts to zoonotic nematodes raw. It's worth noting that wild salmon do have a very high natural prevalence of Anasakid roundworms.. however these aren't microscopic by any means and a sushi chef could easily screen for them.
I think it probably was just about having a consistent, abundant and standardized product rather than highly seasonal and variable wild salmon. You might not be able to beat the right word salmon in the right part of the year if you are are real connoisseur but that isn't amenable to mass consumption. The fat distribution is different as well in a farm raised salmon even if the amount was the same, large visible deposits and it has a very noticable mouth feel and flavour.
Long story short I reckon farm raised salmon took off there for the same reason it has in chain restaurants (cooked) in the US.
It's like facebook/tiktok pitching their platform to an HN crowd and we obsess over security, privacy, social bubble, vision and stuff, turns out no one give a damn. People like scrolling on the phone aimlessly. That's the fatty salmon