From the source:
“Five things on the plane were overdue for maintenance inspections at the time of the crash, including a co-pilot oxygen mask, the NTSB found. An additional 26 problems were noted on the aircraft a month earlier, “including several related to the pressurization and environmental control system,” but the owner chose not to address them, the board reported. Two days before the crash, maintenance workers also saw the pilot’s oxygen mask was missing and oxygen levels were so low that passenger masks would not have worked.”
Wouldn’t a pilot be likely to decline a flight in an aircraft with those violations?