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.
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2011 E90 M3 Monte Carlo Blue
2004 E46 M3 Imola Red