According to a Pew study, millions of dead people are on voter rolls, and an awful lot are still voting. Maybe they left their mail with someone to vote for them.
Covid was the excuse for mail-in voting and a lot of dead people are taking advantage of the relaxation in absentee ballots and mail-in voting. Almost all of them are in swing states.
Rosemary Hoddle got an unsolicited ballot. Rosemary was an elementary teacher, described as a fun-loving person. She died, but her ballot arrived. Somebody found it and voted for her.