Most likely the Trump Administration never knew about it. The story comes from the 1023's the FBI refused to let anybody, including Congress, see. Even though these documents are not classified.
With Hunter's laptop, the testimony of Hunter's former business associate, the 1023s, the discovery of 22 shell companies in the Biden family name and the distinct possibility that Hunter's Ukrainian meetings were taped, the average man on the street would assume something is illegal going on. At least something warranting a Special Prosecutor.
But we don't seem to have that.
What we do have, is an almost entire media blackout on this story. Interesting, isn't it?