It's much more likely that some people knew and journalists went around asking people.
It's surprising how far tittle-tattle can travel.
That's long enough ago that it seems likely that Huang got to know her in her current role. But if the affair started earlier than 2017, there is the suggestion of abuse of power. Not with Powell as victim, but everyone else who hoped to get that role instead of her
1. Stick to the facts - speculation helps no-one.
2. Don't assume to fight on behalf of people you don't know.
For example there appears to be an assumption that his wife has been deeply wronged and she is the victim. This may well be the case. but it also might not be. That part of this story is a private matter for them and not helped by speculation and assumptions.
In fact I'd go further - you have in effect just accused Powell of being promoted by sleeping with the boss based entirely on speculation. Not sure that's helpful either.
My speculation is purely for its explaining or predictive power on the question why all of this is coming out at once, and who's behind revealing all this. I favor the "conspiracy" version (someone wants him gone and exposes his real secrets in the most damaging way). But if we consider that this might all be organically triggered by the revelation of the spy affair we can't discount that the numerically largest group that feels wronged by his affairs might be employees that were disadvantaged whenever affair partners got special treatment