Depends what you mean by “the bubble”. Industry wide, the bubble’s obviously not burst, it’s been inflated many times over. It might be slightly in decline now after the early surge but that’s normal with “new” products (obviously fatbikes aren’t new but they are to a lot of the new customers)
But before, Surly and other fatbike innovator brands were in their own bubble- it was small but it didn’t have many manufacturers in it so they could charge a lot and not worry too much about competition, fast product change etc. That bubble’s burst, now they’re competing with everyone from Halfords to Specialized and Trek and that’s a very different game. And likewise for parts, I suspect sales of Whirlys fell through the floor as SRAM and Raceface got into it, Larrys as soon as Jumbo Jim came along, and so on.
It’s a shame for them tbh, but it’s the nature of the beast when you make a niche succesful, you reap the benefits for a short while then the big guys move in.