Why did you ~ ?
왜 ~한 거야?
1> Why did you break up with him?
2> Why did you drink so much?
3> Why did you decide to quit your job?
1> 왜 그와 헤어졌어?
2> 왜 그렇게 술을 많이 마셨어?
3> 왜 일을 그만두려고 결심한 거야?
Why did you / break up with him?
왜 ~한 거야? / 그와 헤어지다
Why did you / drink so much?
왜 ~한 거야? / 술을 그렇게 많이 마시다
Why did you / decide to / quit your job?