Trump sacrificed himself to create a precedent in constitutional impeachments to fill the hole in the constitutional process.
What is to come with reference to previous public office holders would go at the heart of this issue and likely with a helluva lot more ferocity. It might not have been possible to acquit people in the future because of the pressure on congress. The sacrifice of going through the process will save the constitution and our country from political attacks in the future.
At the same time, McConnell made clear that former office holders can still be responsible criminally and civilly. Watch what fucking happens now, my frens.