Oblivion's Gate reveals that the Novel Verse is a splinter of the Prime Reality and branched off from its parent timeline due to the temporal shenanigans of Star Trek: First Contact. Selecting First Contact as the point of bifurcation between the two canons is not just a clever plot idea, but it's also a fitting choice on a Meta level. While the Novel Verse technically began with the DS9 Relaunch in 2001, it was arguably Peter David's Star Trek: New Frontier that got the ball rolling — and which launched the year after the release of First Contact. The modern Novel Verse was, in its way, born out of First Contact and thus comes full circle for its end.
David Mack also establishes during the First Splinter reveal that the further First Contact and the Original Disruption Point became in the rear view mirror, the more the Novel Verse's timeline diverged from its parent timeline. This not only explains the canonical differences, but also neatly aligns with the real-world literary/TV production from 1996 onward. Again, New Frontier began the year after First Contact. The DS9 Relaunch began in July 2001...right after VOY wrapped and on the cusp of Nemesis. So without having to worry about aligning with any more canonical 24th Century productions until 2020, it's no wonder the Novel Verse diverged so significantly both in-universe and in the real world.
Oblivion's Gate reveals the unique creation and composition of the First Splinter timeline and its branches was what got the attention of the Devidians and set them on the path from becoming cross-temporal scavengers to timeline devourers. Retroactively erasing the Novel Verse and the catalyst for that chain of events is the heroes' Hail Mary for stopping the Temporal Apocalypse. But despite the Original Disruption Event being a one-in-a-million temporal incident, there's still always a chance something like this could happen again. What happens then? What happens if another First Splinter-esque timeline emerges and gets the Devidians interest? This will happen all over again and the sacrifices of the Novelverse heroes will all have been for nothing — unless another reality's heroes make the same discoveries and decisions in time. Hell, for all we know, this has happened before and will happen again.
