이 문장에서 because 절이 it that 강조구문이라고 해설에 나와있는데

it이 앞에있는 agriculture 을 받는다고 해석하면 왜 안될까요?? 도와주세요ㅠㅠㅠ



The most important role of these rivers was in agriculture because it was the ability to grow crops that allowed people to settle in one place.