It all depends in how you view it. If you assume that all these timelines would happen anyway without conscious effort to create them on the part of the Shifters, I guess it makes everything rather moot.
But I generally figure that these timelines still had to be actively created by their participants in order to exist. Yes, multiverse theory posits that every possible outcome for a decision exists out there somewhere, but it doesn't necessarily mean that those decisions just 'happen'. Someone needs to make the decisions in order for the relevant timeline to be created. The real question is why do specific decisions get made?
It's like, if we stick a red door and a blue door in front of Zero, and he chooses to go through the red door....but I needed him to go through the blue door. It's all well and good to say there's a timeline out there where Zero chose the blue door, shrug my shoulders and leave it at that. But then *why* would he choose the blue door over the red door? It's all very well to just assume such a timeline exists, but why does it exist? Does it exist purely because of the vagaries of random chance, or does it exist *because* I set out to engineer a chain of events that ultimately pushed Zero to choose the blue door?
It's a subtle distinction, but important I think.
...Which brings us back to interpreting the game. If you go with the 'everything is going to happen anyway, so meh' outlook, then everything in existence ends up becoming rather pointless. And we end up here:
Meanwhile if you assume a level of conscious interaction required to influence timelines, the plot turns out to be a work of genius. Within a single set of events, Every necessary timeline is created. The one that results in Delta's birth. The one that leads to the Radical-6 ending where Sigma and Phi develop their shifting powers. And of course the golden timeline. In terms of temporal structure, it may be the most brilliantly designed time travel plot I've ever seen.
...But that's only if you give weight to human decisions instead of deciding everything is pointless
I'm not saying every thing just automatically happens, but all of this seems to have been done just to create ONE timeline where the terrorist can MAYBE be stopped, and even that is left super up in the air, because the only thing unique about this timeline is that somehow these 9 (or 8 because the robot?!) humans are now supposedly motivated to stop the terrorist because they went through this ordeal? First I don't even totally understand how that makes sense, I'd probably just get PTSD and be worthless for the rest of my life, but let's say they do all want to stop this really badly now cool but like, what are they going to do, all become FBI agents or something?! What real hopes would they even have? Now, keeping in mind that we're talking about a single timeline, I agree with what Matt said above... someone probably would have already stopped the terrorist in some timeline. Like, this whole series makes a big deal about the fact that a freaking SNAIL can cause such massive changes, so it's not hard to imagine timelines out there where enough changes happened to stop the terrorist.
It's just a sort of bizarre and complicated way to go about creating a scenario that probably already exists somewhere.
No I'm not at all. I'm saying based on the logic of the game, it's highly likely that multiple timelines exist where the big event never happened. Realistically speaking all of the things that would need to be in place for someone to not only become radicalized, but decide to do that kind of attack, have access to the means, pull it off, AND have no one have any idea who did it... there are SO many places in this chain of events that the whole thing could have been thrown off.
Again, this is a series that makes this huge deal out of a snail on the road changing multiple destinies in huge ways. It wouldn't make much sense for this kind of thing to be basically inevitable in all timelines.