1. If the election was limited to in-person, verified (at least by signature) voters, there is a good chance that Trump would have won.
2. In states such as Georgia, where Republicans controlled the voting process, the data clearly indicates both that absentee voters were disproportionately Democratic (perhaps reflect a greater germ-phobia among Democrats), but suggest no one did any ballot box stuffing (since had that been the case, the Republicans would have lost badly in local races, and in fact they di rather well. This suggests that many Republicans chose not to vote for Trump.
3. The Republicans failed to effectively campaign for mail-in votes (similar to how the Democrats in 2016 ignored the “deplorables” )