Agreed, even the President herself is kinda pushing it, even putting herself in danger which would immediately put Darius in that position.
Most people would probably not care about the government, it would probably be chaotic with all that's going on, on top of the threat of a civil war going on.
As for the premise, many pointed out last season how limited the premise was, it's just that the show is turning to Designated Survivor 2.0 tbh.