In the series finale of Game of Thrones, Jon Snow killed Daenerys, but her army of the unsullied just prisoned him, it does not make sense to me. Does it make sense to you also?
The Unsullied wanted to kill Jon, however they are, or were, utterly devoted to Daenerys. Ordinarily this would have meant that they would kill him - there would be no ambiguity and Jon likely confessed and surrendered to them voluntarily.
However, in their devotion to Daenerys, the Unsullied simply don't know what to do with themselves without her. She talked of conquering Westeros, and an army like the Unsullied probably could have made a fair go at it, with or without her or Drogon. However, without her, they are aimless.
Simply put, they don't know what's around the next corner and intend to use both Jon and Tyrion as bargaining chips (Tyrion not so much, since there's not many people around who care about him any more, if there were originally). They are prisoners of war in case the remaining northerners defy them, but ultimately the Unsullied, lacking much of a will of their own, are seemingly content with being left alone to live as they want. They could have killed Jon, and that would have been a perfectly understandable action, but they're waiting to see "where the chips land" essentially.