-는데 sets up an expectation and 끝나다 cuts it off, so the ending lands before the speaker was ready: 시작도 안 했는데 끝났어?, 이제 긴장이 좀 풀어지려고 했는데 끝나버렸습니다, 좀 제대로 집중하고 있었는데 끝나고. Nearly every line here carries that note of an anticlimax. One doubles back on itself: 아 끝난 줄 알았는데 끝난 게 아니었습니다, "I thought it was over, and it wasn't."