I want to agree with you, but civil/criminal rules of evidence do not apply to impeachment. Since impeachment is a political process, high crimes and misdemeanors can be any damn thing the Democrats want to conjur up.
Remember the expression, “He could indict a ham sandwich”?
Grand jury indictments can get crazy as the defendant has no representation. That’s one reason grand jury sessions are supposed to be kept secret. Any nut can make any claim, and the wrongly accused can be stuck with reputational damage.
Impeachment is nothing more than a list of charges, comparable to a grand jury. The Senate trial is definitive. And it’s a Republican Senate deciding on whether high crimes and misdemeanors are at hand.