So there is a clip of someone dropping multiple ballots in a drop box. Apparently [1] that is not necessarily fraudulent, you can drop multiple ballots from family members.
There were international observers in the 2020 election and they found no evidence of fraud [2], and many mainstream media sources that I hold reliable, (e.g. [3]) fact-check multiple claims of election fraud and nothing has showed up that would suggest that the election was "stolen".
I don't think it is at all preposterous to assume that the 2020 US election was fair, unless you subscribe to a view that the global mainstream media apparatus is in on some grand conspiracy.
[1] https://apnews.com/article/fact-check-election-ohio-ballots-...
[2] https://en.wikipedia.org/wiki/2020_United_States_presidentia...