Voter fraud *is* a thing and is a crime. What isn't a thing is vote-by-mail having a substantially higher rate of fraud than vote-in-person. You still have to be registered, your ballot can still not be used more than once, if you request a ballot and it isn't received it can still be flagged, and best of all, paper ballots mailed in or cast in person can be audited far far FAR more reliably than electronic ballots.
The thing about fact checkers is that they tend to use primary sources for their information. If you don't believe the implications, you can dispute those primary sources or the fact-checkers implications. On the other hand, statements that need to be fact checked typically do not cite primary sources, hence the need for validation.