No, Fear and Hunger cannot be purchased or otherwise obtained legally through those channels, nor is it downloadable via Itch.io's site in Germany, as a result of F&H being placed on one of the Listes of banned games — specifically, Liste A, which means that it is hidden from any IP that is trying to obtain it via the Steam Store or downloading from Itch.io.
With a game CD Key, these fine folks, who likely have already paid for the game, can enjoy the game without needing to interact with Steam Store, and thus, be able to enjoy the game.
It took me five minutes to figure this out, it takes zero time to not be an asshole, especially when it involves international censorship laws (doubly so when it comes to Germany, they ban or censor basically everything).