The issue here is the investigation leading to impeachment (formal charges).
The investigation should be done probably by the House IMO and not the DOJ because of prima facia conflict of interest.
You raise a good argument here. What is the purpose of this investigation? Congress very much likes that Comey insinuated (but expressly stated the opposite) a crime might have been committed.
Congress, being 100% risk averse and 80% against Trump was pleased to get the hand up, and went along with the false premise, never stated premise, that a special counsel was necessary, "in order to remove the appearance of bias." Congress wants the Special Counsel to do the dirty work. Same happened in the Fiske/Starr endeavor.
But in order for this approach to be legitimate, there must be a credible allegation of a crime.
If that can't be done, then release the Special Counsel, and put the monkey on Congress.
-- The investigation should be done probably by the House IMO and not the DOJ because of prima facia conflict of interest. --
Congress is per se biased. It's function is to be partisan. Nobody in Congress is unbiased, by definition. But when the point of the investigation is to impeach and remove a president or other official for something that is not a crime, then by golly, it's theirs and theirs alone to have at.