Delta cancels Thanksgiving over Pilot Staffing

Could it be too many Pilots on stay at home orders for partial pay? And no one stepping up for extra flights??
If I had to guess:

Too many flights added by Network Planning after pilots had already bid for the month.
Not enough pilots picking up trips in Open Time.

DL has been pretty surgical about altering the flight schedules once they're published. It hasn't been an issue...until now. Hopefully, they'll learn from it and rebound for Christmas.
I'm sure they will. Reading that many cancellations for the busiest travel day of the year was a shocker to me, especially being it was Delta, they are better managed than that IMO.