This is a huge misrepresentation. They didn't 'allow' mail in votes. Every single state had mail in voting in some shape or form for many years. Some were more restrictive and/or encouraged than others.
That would be right if they are requested without invitation, like so many have done for years.
But, sending out enmass, forms or ballots , leaves room for alot of fraud. Its just a simple fact...
Now, I'm not saying biden didn't win those states but for those looking for room to call biden illegitimate, they have it. Just like Russia and trump.