There's no requirement or need for an actual trial in the Senat

In my opinion, a trial is unnecessary. The House articles, on their face, are defective. Both fail to meet the constitutional threshold of “high crimes and misdemeanors.” This would negate a trial but does not give the president any formal “acquittal,” after a trial on the merits of the articles, which would prove the president’s innocence. While this would be true in a traditional criminal judicial proceeding, it is not the case in a political trial. No matter how the Senate deals with the articles of impeachment, Democrats and Republicans will put their own political spin on the outcome. Since the House articles of impeachment were voted strictly on party lines, and the country is so divided on the whole impeachment process, in my opinion, a trial is less important.

https://thehill.com/opinion/white-house/475755-theres-no-requirement-or-need-for-an-actual-trial-in-the-senate