So by your logic, "nobody wants to investigate" = "voter fraud happened". Sorry buttercup, that's a spurious leap of logic if I've ever seen one.
Ballot harvesting, i.e. having a third party turn in a mail-in ballot, is not an issue. Many states allow this (with some constraints), and there has been no evidence that it contributes to voter fraud. Fun fact: Donald Trump himself had a third party turn in his ballot in Florida. Yet nobody in the pro-fraud crowd has raised concerns about voter fraud in Florida. Why is that? Oh yeah, because Trump won that state! So I guess there's only voter fraud in a swing state if Biden wins it.
70 million people could believe the Earth was flat, and that wouldn't make it any more true. The problem so many on the right are not understanding is that more than 70 million, on both sides, are confident the election was fair and honest, and that's not going away. There hasn't been any evidence to back up any claims of widespread voter fraud in this election.
The math doesn't support a Biden win? What math is that, the one that says the odds of him winning are one in a quadrillion? Yeah, that math doesn't stand up to scrutiny, and that was proven very early on. Or perhaps you're referring to the 100%+ voter turnout? Doesn't exist anywhere in any state election records.
One question I keep asking and the pro-fraud crowd never seems to have an answer: if the Democrats (or whoever you imagine is in on this imaginary, made up voter fraud conspiracy) were capable and/or willing to commit widespread voter fraud, why would they only rig the presidential election? Why would they give so many House seats to the Republicans, and force the Senate into such a close tie that the two Democrat senatorial candidates from Georgia would have to win?