From what I've read, Marty got furious (and rightfully so!) over Activision for changing the soundtrack of some E3 trailer. Apparently, that prompted some, ahem... less than professional reactions on his part, though. I think it's just sad thet had to part ways. There had to be more going on behind the curtains to prompt Bungie to terminate him... Personality conflicts? Financial woes? Whatever the case, there's no doubt in my mind that Destiny is a lesser franchise for that loss.