Backing up a little...
You know that new animated series that they were talking about a few years ago? It took place in a future where multiple Omega-particle detonations had basically split the Federation in half and made warp travel impossible over a large area of space.
Well,
@Christopher made reference to that series-that-never-was in one of his Department of Temporal Investigations novels. Daniels reveals that not only were the Omega explosions caused by Future Guy (from ENT) but also mentions that "If we hadn't been able to isolate that timeline..." He does not elaborate on that last part.
We of course have no idea what they actually did (i.e. what "isolate" means in this sense), but I assume that either the 29th or 31st-century time police managed to do something that took this timeline out of the equation, as it were. Set it aside, so it's no longer part of history.
Maybe the future as seen in DSC is also one of these isolated timelines. It's what I'm hoping for, anyway.