They had eight unfettered years for the rot to set in and do its work.
My theory on Epstein is that he sold blackmail info to the highest bidder—so China probably had the info along with several other countries, companies, wealthy individuals etc.
Epstein may have sold the info a la carte to maximize the profit.
The way that would work—suppose you are a big corporation with an issue before Congress that is a big deal to you (though most people don’t know or care about it).
You pay Epstein for the blackmail info on key Committee chairpeople/members and then work your will.