Complex sentence: The dam owner would have been within his legal rights to dismantle the dam, thereby reducing the lake to a swampy marsh land but instead chose the path of good citizenry and with great generosity agreed to match dollar for dollar all funds raised by the citizens.
Split into simpler sentences: The dam owner would have been within his legal rights to dismantle the dam, thereby reducing the lake to a swampy marsh land. He instead chose the path of good citizenry and with great generosity agreed to match dollar for dollar all funds raised by the citizens.