That's the wrong perspective. The minute votes go into the mail system there is no way to know just how many mail-in votes might be subject to fraud. In other words, your characterization has no basis in evidence. Note that I am not asserting that massive fraud has been committed anywhere. That statement would be as impossible to support with evidence as yours.
The only thing you can state with absolute certainty is that mail-in ballots can be subject to manipulation and that this manipulation can reach enough scale to affect results in elections where the margin is so narrow that a few hundred or a few thousand votes can determine who wins.
Simple example: We receive eight ballots. There's absolutely nothing to prevent me from filling out all eight of them as I see fit and mailing them. Nothing.
There's also nothing to prevent bad actors from destroying ballots in large quantities.
Again, do not mischaracterize my statements here. I am not asserting that any of this has happened. I am saying that mail-in ballots enable potentially serious manipulation and are insecure.
This is like saying that short passwords are insecure. Lots of people use them safely and never get hacked. We all know they are unsafe. The fact that they might not be insecure enough for the general public to understand the issue (because you don't have news every day showing how many thousands of people are getting hurt) is immaterial. The truth of the matter is independent of the perceived consequences. Short passwords are insecure. Mail-in ballots are insecure.