Because in the middle of a speech he was supposed to stop and make a tweet to the Antifa terrorists to stand down, and they would? DC is clearly in an alternate reality.
Mustang Medic, a YouTuber reporting on Capitol news, said while he was attending the speech, CELL SERVICE WAS TURNED OFF...JAMMED DURING PRESIDENT’S SPEECH. He and no one around him had cell service. And he said he also confirmed with Federal officials the cell phones are jammed when President is speaking.
4 minutes in:
https://www.youtube.com/watch?v=Z86FDNt30zc&t=338s
Not sure how far boundaries of the jamming extend; however if that is the case, how could President have tweeted a message to the insurgents (who were already at the capital during his speech) to stop?