I don't understand why Gates would care. He was well known within Microsoft and the Bill and Melinda Gates Foundation for constantly going after female subordinates. Why would this one affair be the straw that broke the camel's back?
Why would an affair linked to a known pedophile pimp be different than going after subordinates? Your guess is as good as mine. (To be clear, Epstein was in fact a known pedophile pimp at this point in time)
How is the affair "linked" to Epstein? As far as I can tell, Epstein merely learned of it and tried to use it as leverage.
Besides, how could Epstein use his own crimes to blackmail someone? If he did somehow procure this woman for Gates, he couldn't reveal that fact without revealing himself as a sex trafficker. That would be a suicide bombing at best.
My theory, it's a leak from gates himself to help distance himself from Epstein and position himself as a victim.
Most don't care about his past relationships and the one who probably did the most divorced him. He had little to lose and some to gain from this getting out.