Between the release of halo reach (the last game the courts gave bungie the rights to make after the trial) bungie was essentially reduced to making half donkey'd ios/android games because they had little to no funding because they took their disgruntled split from Microsoft to court and while I know that in film (due to my degree in progress) that's signing your own death warrant regardless of if you win the trial I can only assume the same applied here. Eventually bungie managed to get Sony and Activision to give them money. I'm willing to bet that they released on xbox due to some pre-split contract (destiny was teased in halo odst as a poster around the city) but this is why bungie gives exclusives to Playstation much like post break-up revenge sex with a sugar daddy.