Here's the problem; in indictments (as an impeachment is...an accusation/indictment, not a conviction) the duty of the prosecution is to prove someone GUILTY.
the Senate decided that the House didn't do the job right, did not allow all the proper investigative procedures, and threw the case out of court because the investigation was, quite frankly, badly done and the accusations simply didn't rise to the height of 'high crimes and misdemeanors.' Yes. It WAS partisan...on both sides, but the Dems started the partisan thing. They've been looking for something, ANYTHING, to impeach Trump over since before the man took office. I haven't seen a single week go by without some left leaning liberal cry 'IMPEACH TRUMP.' Given the obvious....and I do mean obvious...political intent and bias of the whole thing, I wouldn't have impeached him had someone taken pictures of him handing Putin the keys to the Pentagon, given what I know about the false nature of the documents used to cobble this whole thing together. I would simply figure it was photoshopped, and I'd most likely be right.
By the way, it is NOT a tu quoque argument to say that bringing up Biden and his son (and wanting witnesses to their conduct) and pointing out Biden's braggadocio and support from his party for forcing Ukraine to fire a prosecutor for investigating the company his son worked for. A 'tu quoque' fallacy is when someone says that it is perfectly OK to break a law, because his accuser is breaking one as well....like the man who says it is perfectly acceptable for HIM to cheat on his taxes because his accuser cheats, too.
This is not that. What THIS is, is pointing out the hypocrisy of a group of people who are accusing Trump of doing something HE DID NOT DO, even as their precious hope for the future not only DID that thing, but bragged about it.
In other words...WE can do what we want because we are fighting corruption (even though 'fighting corruption' looks VERY much like the corruption they are supposed to be fighting) but we can accuse you of doing something just like it, or worse, and heaven help you if you want to show anybody that this is precisely what you are doing. That is not 'tu quoque,' because 'tu quoque" is a defense based on 'well, of course I can, because you do."
THIS is 'I didn't do it, but YOU did, and now you are projecting." Not 'tu quoque,' but hypocrisy. That the Dems would not allow Biden or his son to testify is absolute proof.