They are blocking the commission, not to prevent us from "finding out," what anyone with a working TV or access to any news source on January 6, 2021, already knows. You have to understand the Trump Cult Logic. If the investigation is conducted by a bi-partisan group, a sense of "fairness," could be associated with the process and its product. On the other hand, the Congressional Committees that would step into the breach and do what the commission was supposed to do, could and would be scrutinized for any hints of partisanship. Even if none were found, any criticism or accusation that was produced in any committee could be labeled as such. Trump and his minions could seize on a word like they did with "collusion" for the special prosecutor's investigation of the 2016 election. They could create a false narrative that the absence of overwhelming proof of this "crime," would confer a blanket "not-guilty," finding for Trump. He prefers these partisan slugfests. He manipulates them to strengthen the commitment of his followers' belief that he is being treated unfairly.