Monday is typically a slow day at WorldCon. For many people, it is a travel day back to wherever they came from. Dealers tend to start packing up early to avoid the crunch at the close of the convention.
When WorldCon was (is?) held on Labor Day weekend, it makes more sense to me, as Monday is a holiday (at least in the U.S.) when people can attend with their family and free from work. On the other hand, by Sunday night, we tend to be pretty wiped out and Monday is a good day to chill, reflect on the Hugos, and maybe get in some last-minute shopping.
Monday for us was mostly logistics and packing (and a lot of carrying boxes to the car). And, at the end, the table was once again the blank black canvas on which we had built our dreams for the weekend.
To everyone I met, and to everyone I saw: Thank you!