But even if they would have tried to do a different ending, people would have been saying how it could of gone this way or that way. The whole games basis is over an infinite possibilities and endless worlds scenario. They could of ended it a million other ways and there would of been an unintentional what if to everything. The way the did in fact end it wasn't just the safest, but also the best way you could end a game based on a theory of infinite worlds. They completely and utterly destroyed those worlds with the main antagonist in it. Not to mention the final scene also sprung in another infinite possibilities of the main Protagonist being alive,