I completely agree that the discussion of impeaching Trump prior to even entering office undermined the actual impeachment. Which is not to say that the Senate would have convicted him regardless.

I also think it is a very dangerous precedent to start prosecuting political leaders. Once you start down that road, you will not achieve agreement on what constitutes a crime worthy of prosecution. Many Trump supporters did indeed want to see Hillary Clinton "locked up". You risk creating a political milieu in which opposing parties lock one another up after the succession of power, which in turn makes it less likely that there will be a peaceful transition. Were the Obama drone strikes illegal? Would that meet the threshold for prosecution? I suspect the answer will in large part depend on the side of the political aisle you are on, which is precisely the danger.