I watched the Dinesh D'Sousa documentary "2000 Mules." (https://2000mules.com/) Although the 90-minute video is maybe 30 minutes longer than it needs to be, it does a very effective job of making the case that the 2020 election was stolen.
It is almost certain that President Biden won the popular vote. However, Presidential elections aren't decided by the popular vote, but by the Electoral College. Because certain "Battle Ground" states were very close, it would have only taken relatively small shifts in five key counties in those states to swing the election. We have heard about some election weirdness in some of those counties, but none of it seemed like it was enough to claim widespread election fraud.
Apparently, there is geo-tracking data available on all of us that can be purchased. An organization called "True The Vote", purchased this data, and claims to have found evidence of widespread "mules" who stuffed election drop boxes with votes. They set a very high bar for what they consider to be "evidence". We have cases of people visiting 30 drop boxes while going back and forth to "non-profit organizations." There is no plausible reason for people to visit so many drop boxes.
Most of these drop boxes only existed because of COVID.
The documentary only has videos of about a half dozen people stuffing drop boxes with votes. This is illegal even if the votes might have been legitimate. Most of these people were wearing rubber gloves so as to not leave fingerprints. They also took photographs of themselves dropping in votes, reportedly because that is how they got paid. The documentary also has a couple of whistle-blowers who explained how the scheme worked. One person's job was to pay the "mules."
Dinesh D'Sousa crunches the numbers, and even by the very high bar for "evidence" set by "True The Vote", the number of votes cast illegally easily would have been enough to sway the election. He also goes into detail about the people who funded these "non-profit organizations."
The documentary also finds people in nursing homes who were too far gone to have voted but somehow voted anyway. One lady in a nursing home said that she didn't want to vote but a nurse made her vote, which is also illegal to coerce someone into voting.
Although I am convinced, my opinion is very much dependent upon the idea that the documentary is telling the truth. I have little reason to doubt it, but I can't rule out the possibility that someone is lying.