A big thing that let them get away with this is that court cases are slow.
So all the lawsuits and investigations, they are still ongoing, and will end up overturning a lot of the snap things that let them get away with stuff.
The deadline was, I assume, for new in person ballots, the ballots brought in via that truck could have been mail in ballots being brought to that place to be counted.
Assuming so, the big problem is probably chain of custody verification.