You can tell that the US presidential election was stolen the same way that you can tell that Covid is being hyped to serve an agenda.  The way you know is that no explanation is permitted other than the official explanation.  

Twitter, Facebook, Youtube, and the presstitute print, TV, and NPR media censor all information that indicates a stolen election. Not even neutral election experts heavily armed with facts, and witnesses who have signed sworn affidavits under penalty of perjury, are interviewed by the presstitute media or permitted to post documentation of electoral fraud on social media.  It is simply out of the question to give any hearing to evidence.  Some Democrats and presstitutes have even called for the arrest of anyone who says Biden did not win or might not have won if the evidence could be weighed.