He was pursuing his vision of AI incluing a chipset specific to LLM processing that would break nvidias hold of the market.
Apparently the BoD didnt like it. They should have just been more forthcoming about it.
Some CEOs would get fired for moonlighting. Others (Elon Musk, etc) build massive companies and make their existing companies more resilient and lasting. The fact that employees closed ranks around him tell you which kind of CEO he is, and the BoD chose to ignore that at their loss