Experience; yes the Omni/Tanker 10 LLC crew is very experienced in the DC-10. To obtain an Inter Agency Initial Attack Card, one most go through extensive training in the fire environment. As well as 100+hrs low level/mountainous terrain, supervised drops, lead plane join ups, all of which takes at least two season to obtain. All of wich the DC-10 crew did not posess, and it showed.
DC4boy is being exceptionally generous to the DC10 crew, in a tactful manner. While it's possible, technically, to obtain a card within those times...typically one is over fires for ten years before being able to act as PIC in a tanker.
Being qualified to fly a stable instrument approach on breezy day to a nice, long instrument runway is not the same as flying a drop in the mountains in high winds, severe turbulence, low visibility, with high traffic density, when others are counting on you and the taxpayer is footing the bill. Simply because one is qualified to fly the airplane does NOT mean one is qualified to fight fire with it.
Flying the airplane is just a small part of using it to fight fires.