Many of these radical proposals are supported by some radical environmental groups like the Center for Biodiversity.
Their members will flood the federal registry comment page with support for the ruling. Most of the members are not scientist but rather librarians, business people, school teachers etc.
If they don't get their way the sue the USFWS and often win.
When USFWS starts one of these proposals they always get their way.
A few years ago they put common snapping turtles on the CITES endangered species list, even though every species monitoring agency listed them as "Of lest concern" of similar.
When this was pointed out to the USFWS via comment on The federal registry they simply answered that they have their own methods of determining weather the species is threatened or not and gave no explanation.
That response was a direct violation of the endangered species act, that requires independent professional research.
In short, USFWS is an authoritarian organization that basically dose whatever they want.
If they propose a rule, you can be sure it'll be instituted.