...the snail darter, ... the opposition to this project was beaten in court ...
As explained in post 3 above, and the linked article, the snail darter supporters who opposed the dam won in court. They lost to the government, specifically Congress and the prez, and the dam was built.
...the spotted owl ... were supposedly on the verge of extinction at the time. Thirty years later there are enough of them that they are only considered a "threatened" species - and they have been found living in people's barns...
The spotted owl remains in decline. The threat to the species is now said to be the barred owl, a very similar species, which has spread beyond its former stomping grounds — east coast, IIRC — and into the PNW. Barred owls like the same environment, same food, etc., as the spotted owls and are better at competing for resources. In consequence, the spotted owls are dwindling in number and continuing to approach extinction.
The plan to save the spotted owl from extinction, supported by the government and environmentalists — but not without controversy — is to reduce the number of barred owls by selectively shooting them so that the spotted owl can survive.
To me, seems a little rough on the barred owl.