If that is the case, it's a very different claim than that AI is plagiarizing Tailwind (which was somewhat of a reach, given the permissiveness of the project's MIT license). Achieving such mass adoption would typically be considered the best case scenario for an open source project, not harm inflicted upon the project by its users or the tools that promoted it.
The problem Tailwind is running into isn't that anything has been stolen from them, as far as I can tell. It's that the market value of certain categories of expertise is dropping due to dramatically scaled up supply — which is basically good in principle, but can have all sorts of positive and negative consequences at the individual level. It's as if we suddenly had a huge glut of low-cost housing: clearly a social good on balance, but as with any market disruption there would be winners and losers.
If Tailwind's primary business is no longer as competitive as it once was, they may need to adapt or pivot. That doesn't necessarily mean that they're a victim of wrongdoing, or that they themselves did anything wrong. GenAI was simply a black swan event. As a certain captain once said, "It is possible to commit no mistakes and still lose. That is not a weakness; that is life.".