One possible reason why the Supreme Court intervened in some state cases, but not others:

The difference appears to be that a majority of the Justices are unwilling to disturb *state court* rulings with respect to deadlines for receipt of mail-in ballots, but willing to intervene where it’s only because of a *federal* court’s intervention that the deadline changed. https://t.co/0HLroU8ULK

— Steve Vladeck (@steve_vladeck) October 28, 2020