ESA was first enforced on the Charismatic Megafauna. Basically, mammals and birds that nobody "used" anymore and whose retention caused rather minimal disruption to us. I am speaking about ESA in the US as we seem to discount locals when "saving" elephants, lions, and tigers.

Where ESA ran into problems was when it conflicted with the economy. Snail Darters, vernal pool inverts, Sagehens, and resources that meant important people (read campaign donors) would have to change their ways.

Salmon are the poster child for impacting too many important people. They need reasonably intact watersheds (logging, mining, hydropower, agriculture, manufacturing, domestic water), they need intact ocean systems (forage fish, proper temperatures and currents, lack of toxics), and song controls on predation (SRKWs, pinnipeds, humans). Too many of those activities impact too many people who have power.