The reasoning, and I'm not saying that I agree with it, is that Seiko has recently been jacking up their prices without really improving their product.
For a long time Seiko has been on par with Citizen in that mid-tier watch range. Recently, Seiko's management decided they wanted to move up a tier and be seen as competition for Tissot/Hamilton (chasing would-be Swiss buyers). They took the chance during the transition from the 7S26 movements (found in the old Seiko 5 SKXs, which you used to be able to get for ~$150 or so) to the 4R36 movement which added hacking/hand-winding. Now Seiko 5's go for $400 MSRP, with the same Hardlex crystal, a decreased water resistance of 100m, very cheap pressed-clasp bracelets, and a movement with +45/-35s accuracy. In other words they're heavily overpriced now.
Long Island saw the chance to fill the void Seiko left behind (Orient has done this too, to an extent) and started to release their own watches. They deliberately use Seiko's designs and movements, but with sapphire crystal and 200m water resistance. They want that segment of buyers who are disgruntled with Seiko's price hikes and want similar-looking alternatives at better price points.
Edit: This is a $575 watch with a Hardlex crystal. What are you doing, Seiko.