The main motivation is to make open models only work using CUDA. Once models work on AMD, Intel, or Tenstorrent, it might genuinely be over.
Also, I've heard many western labs use open source CUDA kernels (usually from Chinese labs), IMO it makes little sense to move away from CUDA right now unless you're a big player that can afford a patchy ecosystem with internal development (e.g. Anthropic with JAX/TPU).
Most models have moved to MoE and expert routing which is done over infiniband, so tensor parallelism where Tenstorrent was really weak at isn't used much, I can see it as a viable alternative where latency isn't a concern but cost is.
Also even if they wanted to increase the capacity on their GDDR, they wouldn't be able to since they are limited by the GPU memory channels.