Here's my guess.
COTA found more profitable events. Think of all the races coming up. Then this is a new track so teams have to do more testing to create some data points. FYI...Turner and Bimmerwold were in town recently. AND...F1 is THE priority. I don't see how a DE is profitable at this point since they have to keep the facility in top condition. Let's face it...how much oil and coolant gets dragged around the track over time? I can still see my oil trail at Cresson in Rattlesnake when my engine let go.
I am disappointed but I don't blame COTA. Its about track survival which is good for us. It increases the chances that the track will survive.
2013 F30 328i Melbourne Red
2011 E90 M3 Monte Carlo Blue
2004 E46 M3 Imola Red