Well, the reasons the story goes down is because it had too slow of a start--you have a huge boost here when you start. And it has this slow start not because of the other creators, but because it doesn't capture the silent readers.
My current book, my projection was 50 subs. I managed to gain 125 instead, mostly in that second week peak, when it got the boost from the initial start up. I was surprised, because it was not a fantasy and not high school. It got extra exposure with Staff Pick, and you can clearly see it slurping up that pool as well till it emptied in 3-4 days, getting capture, but not snowballing.
Why? Because it doesn't have high growth potential. So, it levels off earlier than more in-tune with tastes fictions. It is absolutely in the book itself.
When I am thinking of my next project, I am looking at its pro's and con's vs audience interest like this:
Werewolves--big win, but it is not werewolf right away, in your face. Most people won't even make it to werewolf part. Must emphasize in Summary and on the cover.
Foreign setting, foreign main character--HUGE drawback. Huge. This will sink me
BL main couple--good, but runs against a lot of fictions that have faster, more salacious BL. Depends on my luck or my mastery
Starts in a school, has a music idol--that's all pluses
but develops away from the school, has intricate lore--HUGE minus
My overall assessment: 75-90% chance of staying under 100 subs, 5% chance to end with about 125-150 range, 5% chance to stay under 25 subs. One lucky card to hit 250. No chance to get over that.