And he says that he never would have become such an expert
in the first place had he not been too introverted to leave the house when he was growing up.
그리고 그는 자랄 때 너무 내성적이어서 집을 떠날 수 없어 그런 전문가가 되지 못 할 줄 알았다고 말하더군요.
뒷부분이 어떤 구조인가요? in the first place 다음의 had는 어떻게 이해해야 하나요?;;