Complex sentence: Thus, nominally at peace, full of wealthy proprietors, and exporting corn largely every year, Sicily was nonetheless teeming with evils, which, seventy or eighty years after, broke out in the horrible atrocities of the Servile War.
Split into simpler sentences: Thus, nominally at peace, full of wealthy proprietors, and exporting grain in larger quantities every year, Sicily was nonetheless teeming with evils. After seventy or eighty years, pressures broke out in the horrible atrocities of the Servile War.