If you are referring to Ex. Ord. No. 14019, note when it was issued (March 2021) and the fact that it's an EO, not legislative statute. Biden's unconstitutional "order" doesn't mean shit in the legal sense. Even IF one was to argue that the EO is authoritative, again note the date... thems not the rules for 2020.

Show me where under US Code, universal mail-in voting is permitted?

Election day, is election day. Not days, not weeks, not months. Ballots are only valid if cast on the day proscribed by US Code, unless it qualifies as absentee ballot. All absentee ballots are mail-in ballots, but not all mail-in ballots qualify as absentee ballots. See WI and DE high courts recent rulings on the matter.

Trump avoided challenging rules changes in court before the election.

Efforts were made, albeit not strong enough ones. My guess is that the strategy was to catch illegal activity and challenge it, then show your hand and attempt to prevent it.

If you are referring to Ex. Ord. No. 14019, note when it was issued (March 2021) and the fact that it's an EO, not legislative statute. Biden's unconstitutional "order" doesn't mean shit in the legal sense. Even IF one was to argue that the EO is authoritative, again note the date... thems not the rules for 2020.

Election day, is election day. Not days, not weeks, not months. Ballots are only valid if cast on the day proscribed by US Code, unless it qualifies as absentee ballot. All absentee ballots are mail in ballots, but not all mail in ballots qualify as absentee ballots. See WI and DE high courts recent rulings on the matter.

Trump avoided challenging rules changes in court before the election.

Efforts were made, albeit not strong enough ones. My guess is that the strategy was to catch illegal activity and challenge it, then show your hand and attempt to prevent it.