Before we do that, why don't we test your knowledge of what "credible studies" means. As per usual KF, you like to make it up as you go.
You have heard of the Carter-Baker Commission, I presume? And to nip your predictable reply in the bud, president Carter had called for an increase in voting by mail for the 2020 election, but only if the inherent opportunities for fraud in voting by mail were addressed. Nobody would say that Philadelphia, birth place of our nation, is a paradigm of political fairness.
From the Carter Center, comes this:
"The nonpartisan 2005 Commission on Federal Election Reform, co-chaired by former U.S. President Jimmy Carter and former Secretary of State James A. Baker III, noted among its many findings and recommendations that because it takes place outside the regulated environment of local polling locations, voting by mail creates increased logistical challenges and the potential for vote fraud, especially if safeguards are lacking or when candidates or political party activists are allowed to handle mail-in or absentee ballots."
The last half of that last sentence should not be lost on anyone, particularly you. Though it clearly has been.
I'm not saying the fraud was on a scale significant enough to change the outcome of the 2020 election, but there's certainly that possibility. If Trump's lawyers can't prove it, then it doesn't matter if it happened or not.
I'm sure you don't recall that I boldly predicted (see what I did there? hehehe... boldly...) before the election that the opportunity for voter fraud was so significant, that whichever side was better at cheating would be the winner. It's pretty clear which side is better at cheating.