One answer is because it was yet another way to denounce President Trump to create the impression that he is unprepared and thus not fit to lead. After all it is an election year, and all other attempts to remove him have failed.
Too bad they are running down yet another parallel path as the paths previously taken. 8>)
Another answer is the conflicting reports out of China itself, and the inability to ascertain the truth.
Or a combination of both.
I'll go with C, with a heavy emphasis on A,& B, leading to C. 8>)
I think of it as “Parallel Construction “
They are creating false narratives and feeding to sources that should be unimpeachable but, fail for the origination story...
Truth is: “It’s Hoaxless” hysteria...