It’s hard to tell.
But your meal sounds pretty fatty. Fat slows down the absorption of carbs. So it may have been the cheese, fat from meat and oil the fries were cooked in rather than the Diet Coke which helped you.
Incidentally, some time back, I read about the effect of Diet Coke on people without diabetes: some of them are experiencing hypos. This is because the body is confused by the sweet taste of the coke so releases insulin but there are no carbs for the insulin. I don’t know the details. It may have been large amounts of Diet Coke without any food. But i found it slightly worrying.