Complex sentence: Among his main debtors were often owners of sugar factories in East Java and when these factories were unable to repay the loans, due to the long-lasting effects of the sugar crisis of the 1880s he used his rights as a creditor.
Split into simpler sentences: Among his main debtors were often owners of sugar factories in East Java. When these factories were unable to repay the loans due to the long-lasting effects of the sugar crisis of the 1880s, he used his rights as a creditor.