Complex sentence: For this reason, the wreck site and the event itself is very important to the community of the lower Yorke Peninsula, not only because of the disastrous loss of life, but also because they played a major role in aiding the survivors.
Split into simpler sentences: For this reason, the wreck site and the event itself is very important to the community of the lower Yorke Peninsula. Not only because of the disastrous loss of life, but also because they played a major role in aiding the survivors.