2. Season 2 was for quite some time available, but it was clearly visible, and stood that these should be available only to a certain date. Amazon had acquired the exclusive rights for the German premiere. After that was a few months available then the series has been taken on the date stated already far in advance out of the program because the exclusive rights covering only this time the first showing.
There are at Prime also many other (exclusive) titles that are only available for a certain time always. This is then available in orange font with the movie "XX days yet available. Available until [date]".
However, I think that the season will be available at Prime again in the future, most likely after alleridngs Blu Ray release. But I do not know exactly, and is just a guess.