I'm all for having CEOs take responsibility. But unless it comes out that he actually leaked anything of substance than it really doesn't matter that he cheated on his wife from the business perspective.
It could still be an issue if his wife divorces him, takes a significant portion of his stock and decides to sell it off. The NVIDIA board would have to consider that possibility.
One could certainly question his judgment. As CEO of Nvidia, he should have recognized that his position made him an exceptionally valuable target for foreign intelligence operations