Do you really think this is the same as sleeping with a random person at a company which happens to use some Nvidia products?
When former Intel CEO Brian Kraznich did it he was on the chopping block and they used as an excuse to fire him.
But Nvidia's board has a history of being favorable to Jensen-- he hasn't done much wrong and typically they will reward performance. First responsibility is share-holders but there is a lot of self-interest at play. If they don't fire him they could face action by government or get sued by shareholders, if they do fire him they deflate the value of the share holdings further.
Now that Nvidia has blown up so much they think they can do fine without him -- but it can easily turn into the next Intel. It most likely won't 100x in two years but it can certainly crash if there are poor decisions made. If the CFO is rumored to replace him, changing leader from a founder engineer to a finance person isn't likely to go well.
But not with his employees or staff at companies he sells to, he’s the CEO of one of the biggest companies in the world, being paid billions, it’s not a big ask.
Random low level managers in a supermarket have been fired for sleeping with their staff.