I'm sure this has been answered several times but you know what? In all these years they have been with Microsoft, I never knew why Nintendo would pull something so stupid as to sell one of their best development companies. I mean honestly, do characters like Joanna Dark, Conker and Banjo seem right on an Xbox console to you? No, these seemed all Nintendo to me. Its like seeing Mario on a Playstation... it wouldn't work. All these years of missing good franchises we could of had on the Gamecube like Perfect Dark and Killer Instinct, I never knew why Nintendo sold Rare! But why did they!? There must of been a really good reason.
Nintendo never actually owned Rare. They just used to have a really close relationship. Microsoft happened to see a prime business opportunity and acted, that is all. I know, it sucks for us DK fans, but there is not much we can do now : /