The Narada incursion had the benefit of three things - a black hole, a very intense ion storm, and the magical red matter. We can minimally accept that as a unique confluence of events that led to a branched rather than overwritten timeline, at least.
To support the resilient river of time model, when I was studying history in grad school I came up with this axiom: history isn’t inevitable, but it has momentum.
To put another way, any given historical event is the natural outcome of historical events before it, and therefore when changing history you’re not just trying to change the one thing, but dealing with the weight of everything before pushing the timeline in that direction. That’s why it’s so hard to change history, that - in Sera’s terms - it seems like Time itself is fighting you. Call it historical momentum, call it historical inertia, what you will. And so the more “momentous” the event, the harder it is to just change it - things will “want” to go back to the way it was.