I understand why they turned it down and its unfortunate because they will never get another chance at that much money.
Look at it this way - You really want to buy a new car but you know that you won't get accepted for financing so why even start the process.
Groupon knows that it would either not go through, or would cause a lot of trouble and time to make go through, so its just not worth the fuss.
I guess they are hoping someone else will step up that will make purchasing easier and/or they will just continue to make the money they make now.
Just my two cents