[quote name='PyroGamer']Microsoft MADE Bungie who they are today.
I wonder why Bungie wants to sever the ties now.[/QUOTE]
daroga addressed the first point, but I have to say that in hindsight, we forget how gamers generally bristled at the idea of MS entering the console market. Moreover, Halo was all the Xbox had in the early days (XBOX HAS NOE GAMEZ!!!). Without Halo, MS would be in a very different spot than they are now.
Those of us who bought Marathon on release day, or have played through Pathways Into Darkness, know just how good of a developer Bungie was years before Halo.
As for why Bungie wants independence, my guess is twofold: (1) they earned their money, and (2) they don't want to be a Halo factory the rest of their lives.