I think you couldn't stop it because a lot of people probably expect a full release/1.0 version of a game to have a complete story line to some extend. I don't know what's going on behind the scenes, but calling this patch 1.0 was an odd decision imo.
The vast majority of the feedback that we get tells us very clearly that end game content is dramatically more valuable overall than story content. So leading up to 1.0, that was our main focus. 1.0 was the first version where we had all of our planned classes available and our end game was feeling like a proper end game set of systems.
With a live service model game, the story will always be expanding and evolving. It's hard to draw a line and say that at any one point is where the story is "ready for release".
We considered many scenarios and plans for a path to 1.0 in very specific detail. We are very pleased with our decision and hindsight being 20/20, I would do it again just the same.