If you dissect the timeline of the events and various statements, I think the 2nd affair with a subordinate employee K Powell was the reason to fire Jensen Huang -- more so than the allegations of secretly selling to China.
This is the timeline:
Nov 8 : Jensen issues apology. NVIDIA allows him to use nvidia.com for this
Nov 8 : The Board of Directors publicly backs him up with a "vote of confidence" by stating: *"no reason to believe that either national security or NVIDIA secrets were compromised" and that "The Board has confidence in Jensen and his leadership team."* -- from https://nvidianews.nvidia.com/news/statement-from-nvidia-board-of-directors
Nov 11 : 2nd affair gets exposed in the news
Nov 11 evening : emergency meeting of Board of Directors is called to fire Jensen Huang
Before Nov 11, it looked like NVIDIA might try to ride out the storm and keep Jensen at the helm especially if they saw that the China accusations and evidence wasn't strong enough to be a problem. Again, it was totally unnecessary for the board to publicly back him up if they had plans to get rid of him because of China allegations. However, the Board of Directors emergency Nov 11 meeting is inconsistent with the Nov 8 statement affirming Jensen's leadership.Nov 8 was coordinated with carefully crafted communications showing that Jensen and BOD were aligned. Contrast with Nov 11 being chaos and an emergency meeting convened.
Reading between the lines, what probably happened is that Jensen didn't come totally clean with the board on Nov 8 and tell them about the 2nd K Powell affair. Instead, the board got totally blindsided and lost trust in him. (Is there another 3rd secret affair he's hiding from us?!?) It was impossible to keep Jensen under those circumstances.