The Shadowrun timeline actually splits off in 1989 when the first edition was published. The USSR didn't fall, 9/11 and its aftermath didn't happen etc. That's not to say the universe makes any kind of internal sense (although "this is just how white American dudes from 1989 who like hermetic esotericism to an unhealthy degree saw the future" makes tons of sense from an outgame perspective), but i've learned long ago that trying to write a "realistic" alternate timeline for Shadowrun isn't exactly an easy task, especially when you want to still arrive at something that's recognizably Shadowrun while also weeding out the more problematic undertones of the setting like the racist brainworms behind the portrayals of Japan and Aztlan or how they gloss over anything outside of with "i guess it's poor and most of the people there died from VITAS." When we're being realistic, we know perfectly well who'd be hit hardest by a pandemic that kills off a quarter of the world population. You can work that all into the setting, but at that point you may as well run with an original idea and turn that into a setting, it's just as much work and less headache.