Honestly, I dont really think it is any sort of conspiracy or glitch with the system...I just think demand is off the charts. Early December is already one of the most popular weeks of the year and there's a glut of points in the system so I'd think:
a) More people are planning to travel in late 2021 after likely not visiting in 2020
b) More people have "extra" points, allowing them to stay longer and/or in larger rooms (i.e., 1BR rather than a studio)
c) More people are walking reservations to give them a better shot at the reservation they want
If you look at some of the other threads, it sounds as though availability in November/December is tight across the board.