CS prof since 2000 here. We saw similar numbers at my school. I imagine the explanation is something like what you suggest. Note, by the way, that we might be

CS prof since 2000 here. We saw similar numbers at my school. I imagine the explanation is something like what you suggest. Note, by the way, that we might be a bit less pessimistic than your "just stayed to complete their degree". The bubble drove a great deal of publicity concerning computer programming; the result was an increased interest. And that interest remained even after the bubble popped.