Anyone who has ever watched a procedural cop show or has any dealing with the legal system knows the importance of protecting evidence from any form of corruption. If evidence is tainted by even a hint of coercion it can never be used.
This is the simple reason why investigators spend an inordinate amount of time and effort to validate a piece of evidence before they confront a suspect or a witness. In this way they can be certain that the witness or suspect’s answers to any question are not being influenced by any other elements (such as being paid for their views or pressured to give a specific answer), and they can prove it when it is presented in a legal proceeding.
If the White House had truly believed that a previous administration had used either undue influence to take a position on foreign company boards or to protect their interests in foreign companies by applying government policy in ways that rewarded members of their family then they should have asked the justice department to investigate. If course that very investigation would have quickly extended to include the business interests of the current Presidents family and their actions during this current term.
What the President could not have done, is exactly what he did do. He could not ask the leader of a county (or multiple leaders of multiple countries) which we are directly working with, to investigate the previous actions of American citizens, because there is absolutely no way that such a request could not be tainted with influence, and therefore cannot be accepted as evidence.
It was the act of what the Irish should term “a firkin idjot”
So Maybe we should rename the acronym for the leader of the free world from POTUS to FIOTUS