Differentiating between "there was fraud" and "there was centrally organized fraud of such a magnitude as to swing the election."
In any case: universal suffrage on the scale of the US population, combined with the reach of mass media and facebook-assisted individually targeted advertising, adds up to antipopular despotism. The hazard of enfranchising vast herds of stupid adults isn't well-intentioned poor decision-making, but easily manipulated decision-making. That the source of disillusionment with our system is, for many, a perception of procedural fraud rather than its failure to serve the people, itself further serves the regime, as a distraction and as a charge which is answerable with promises of reform.
Electoral procedure can be reformed, but there is no solution to the ever-increasing ability of the powerful to manipulate the stupid. Right now, someone is probably shoving Facebook data into an algorithm that can turn the midterms on ads and reordered search results: what is "election fraud" then?
I only wish your analysis helped. As you note something on such a scale would require considerable organization. So we see that https://time.com/5936036/secret-2020-election-campaign/ by Molly Ball. In that article the legal changes assisted in how ballots were used. Such an effort took a lot of money and effort. Getting the cooperation of the Chamber and the AFL/CIO was quite an accomplishment. So businesses were somewhat coerced into cooperation by the implied protest threats. And then the election observers were limited by more coercive threats to election officials. Nor much of a stretch to imagine the Time election group seeing 538 maps and creating enough ballots to gain an advantage exactly where the advantage was needed. Money and organization were obviously in place. So I can't just let those facts go away.
In contrast, if we examine that no defense was mounted against changes in the election rules, we see a political party not particularly interested in re-election of their own President. Observers not allowed to observe should have had US Marshals on stand-by to require adequate surveillance. Counting should not have preceded without observers. Perhaps the scale of the effort was unknown to the Republicans but that remains unclear as well. Perhaps the Republicans are, in fact, that clueless.
At any rate, Mr Biden played rope-a-dope well. Mr Obama has managed to hold his team together, at least until the next election. Everybody understands that turning the DC huge morass is a terribly slow process. But the election has left a bad taste behind that the public is not particularly happy about, at least the part who even care about politics.