Soundwave on 10 September 2015
Because they though the XBox One could be their magical convergence device that they missed the boat on when they let Apple beat them to the smartphone and tablet.
So XBox One I think was their hope that it would be the "iPhone of the living room", aka: the one device that does everything you need in that area.
Also if you know the history of the XBox, the XBox was always supposed to be like a living room set top box, not just a game console. In fact, Bill Gates was not happy when the original XBox was streamlined down to more of a traditional console that didn't actually run full Windows.
