The attackers were antifa. Right wingers had nothing to gain by stopping the presentation of fraud evidence.
There was a thread posted here on FR about a week before the rally that talked about ANTIFA making plans to infiltrate the Trump rally, wearing MAGA hats and the like. The main purpose was to start a “riot” that could be blamed on Trump supporters.
The thread included Twitter postings giving specific information about how ANTIFA planned to cause a problem. If it was posted here in advance, you can damn well be assured the authorities were aware of it as well.
This has Reichstag fire written all over it. Of course, by now Twitter has removed all the evidence from their forum to protect the left.