they were so important to the indians that they thought of their horses as aprt of the family. it was as an indian horse that the mustang gained its greatest fame

두번째 문장 it ~ that 구문이 어떤 의미로 쓰인건지 잘 모르겠어서 질문드려요.

it ~ that 강조구문으로 사용된 게 맞는건지요?