Of course we know. It was investigated by Twice Impeached Trump’s own Department of Justice.
“to date, we have not seen fraud on a scale that could have effected a different outcome in the election.” ~ William Barr, former Attorney General
Which is dumb. It is silly to think that all fraud was found.
The point is the widespread fraud is done for a reason. TO effect an outcome in the election.
Evidence of widespread fraud indicates the need for more information.
Trump has been claiming the system is rigged against him for 40 years.. This crap isn't new for him.