Roads at some point in the journey are not passable.
For example, Bismarck hub at one point was 136 trailers behind this month. Interstate coming in and out was not drivable. All their trailers were getting weather exceptions. So there were trailers in CACH, SLC, Omaha, etc that were sitting on their property, because the meet points where they'd drop the trailers no longer had room for them. I know when I was out in Minny, they said Fargo had 55 trailers sitting on property for Bismarck.
Trust me, I know.
The OP felt that the only problem was at one point. Could have been anywhere along the projected path.
An emergency situation also could have been anything from a mechanical breakdown to an accident on a major highway.
But, people gotta get their crap just as soon as they order it.