The one thing our Founders didn’t predict, or didn’t properly account for, was the development of partisan politics and, as a result, how hyperpartisan the impeachment process would become.
It takes the votes of 2/3 of the Senate to remove an impeached president. After Ukrainegate and the failed impeachment that resulted, it is hard to imagine any presidential conduct that would ever meet that standard. In addition to the holistic obstruction that prevented the House from fully investigating the charges, obstruction which was rubber-stamped by the GOP Senate.
No witnesses were called by the Senate. Trump himself never testified or even showed his face on the Senate floor. Indeed it was a joke of an impeachment trial, but not for the reasons you are probably thinking.
Impeachment is a dead-letter provision of the Constitution until we one day get a new Constitutional Amendment to clarify processes. Otherwise, all future Presidents will simply figuratively crumple up and toss aside any impeachment articles thrown their way, and their own parties will let them do it.