Read it.
And excerpt:
In a grievous betrayal of his Oath of Office, President Trump incited a violent mob to attack the United States Capitol during the Joint Session, thus impeding Congress’s confirmation of Joseph R. Biden, Jr. as the winner of the presidential election.As it stormed the Capitol, the mob yelled out“President Trump Sent Us,” “Hang Mike Pence,” and “Traitor Traitor Traitor.”The insurrectionists assaulted police officers with weapon sand chemical agents. They seized control of the Senate chamber floor, the Office of the Speaker of the House, and major sections of the Capitol complex. Members and their staffs were trapped and terrorized. Many officials (including the Vice President himself) barely escaped the rioters. The line of succession to the Presidency was endangered. Our seat of government was violated, vandalized,and desecrated. Congress’s counting of electoral votes was delayed until nightfall and not completed until 4 AM.Hundreds of people were injured in the assault. Five people—including a Capitol Police officer—died.
Trump's mob attacked the Capitol to stop the Congress from confirming Joe Biden as president.
It's that simple.
If that's not treason then there is no treason.
